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Biomedical subjects

J G Lewis

Publications and source records attributed to J G Lewis.

At least 19 recordsLinked to original sources
PubMed2006

Plasma variation of corticosteroid-binding globulin and sex hormone-binding globulin.

Sex hormone-binding globulin (SHBG) and corticosteroid-binding globulin (CBG) circulate in plasma and bind their cognate ligands with high affinity, offering a steroid delivery system to target tissues by a variety of mechanisms. Analysis of these steroid-binding proteins is gaining importance in the clinical setting, although more information is warranted on their diurnal and biological variation. This study shows that plasma SHBG (in normal subjects) exhibits little diurnal or biological variation over the 30 day period studied, in contrast to CBG, where plasma levels peak in the early afternoon. This leads to attenuation of the diurnal free cortisol level rhythm compared to total cortisol. We also show that plasma CBG is significantly lower in male subjects with the metabolic syndrome compared to age-matched lean counterparts, and may therefore act as a surrogate marker of insulin resistance. The consequence of lower levels of CBG in these obese male subjects is reflected by higher levels of circulating free cortisol, potentially offering a more favourable environment for adipogenesis.

Adult↗
PubMed2006

Expression of corticosteroid-binding protein in the human hypothalamus, co-localization with oxytocin and vasopressin.

Corticosteroid-binding globulin, a specific steroid carrier in serum with high binding affinity for glucocorticoids, is expressed in various tissues. In the present study, we describe the immunocytochemical distribution of this protein in neurons and nerve fibers in the human hypothalamus. CBG immunoreactive perikarya and fibers were observed in the paraventricular, supraoptic, and sexual dimorphic nuclei in the perifornical region, as well as in the lateral hypothalamic and medial preoptic areas, the region of the diagonal band, suprachiasmatic and ventromedial nuclei, bed nucleus of the stria terminalis and some epithelial cells from the choroid plexus and ependymal cells. Stained fibers occurred in the median eminence and infundibulum. Double immunostaining revealed a partial co-localization of corticosteroid-binding globulin with oxytocin and, to a lesser extent, with vasopressin in the paraventricular and the supraoptic nuclei. Double immunofluorescence staining showed coexistence of these substances in axonal varicosities in the median eminence. We conclude that neurons of the human hypothalamus are capable of expressing corticosteroid-binding globulin, in part co-localized with the classical neurohypophyseal hormones. The distribution of CBG immunoreactive neurons, which is widespread but limited to specific nuclei, indicates that CBG has many physiological functions that may include neuroendocrine regulation and stress response.

Aged↗
PubMed2005

Septic shock and sepsis: a comparison of total and free plasma cortisol levels.

CONTEXT: Severe systemic infection leads to hypercortisolism. Reduced cortisol binding proteins may accentuate the free cortisol elevations seen in systemic infection. Recently, low total cortisol increments after tetracosactrin have been associated with increased mortality and hemodynamic responsiveness to exogenous hydrocortisone in septic shock (SS), a phenomenon termed by some investigators as relative adrenal insufficiency (RAI). HYPOTHESIS: Free plasma cortisol may correspond more closely to illness severity than total cortisol, comparing SS and sepsis (S). DESIGN: This was a prospective study. SETTING: This study took place in a tertiary teaching hospital. PATIENTS: Patients had SS (n = 45) or S (n = 19) or were healthy controls (HCs; n = 10). AIM: The aim of the study was to compare total with free cortisol, measured directly and estimated by Coolens' method, corticosteroid-binding globulin (CBG), and albumin in patients with SS (with and without RAI) and S during acute illness, recovery, and convalescence. RESULTS: Comparing SS, S, and HC subjects, free cortisol levels reflected illness severity more closely than total cortisol (basal free cortisol, SS, 186 vs. S, 29 vs. HC, 13 nmol/liter, P < 0.001 compared with basal total cortisol, SS, 880 vs. S, 417 vs. HC, 352 nmol/liter, P < 0.001). Stimulated free cortisol increments varied greatly with illness category (SS, 192 vs. S, 115 vs. HC, 59 nmol/liter, P = 0.004), whereas total cortisol increments did not (SS, 474 vs. S, 576 vs. HC, 524 nmol/liter, P = 0.013). The lack of increase in total cortisol with illness severity is due to lower CBG and albumin. One third of patients with SS (15 of 45) but no S patients met a recently described criterion for RAI (total cortisol increment after tetracosactrin < or = 248 nmol/liter). RAI patients had higher basal total cortisol (1157 vs. 756 nmol/liter; P = 0.028) and basal free cortisol (287 vs. 140 nmol/liter; P = 0.017) than non-RAI patients. Mean cortisol increments in RAI were lower (total, 99 vs. 648 nmol/liter, P < 0.001; free, 59 vs. 252 nmol/liter, P < 0.001). These differences were not due to altered CBG or albumin levels. Free cortisol levels normalized more promptly than total cortisol in convalescence. Calculated free cortisol by Coolens' method compared closely with measured free cortisol. CONCLUSIONS: Free cortisol is likely to be a better guide to cortisolemia in systemic infection because it corresponds more closely to illness severity. The attenuated cortisol increment after tetracosactrin in RAI is not due to low cortisol-binding proteins. Free cortisol levels can be determined reliably using total cortisol and CBG levels.

Adrenal Insufficiency↗
PubMed2005

Circulating levels of isoflavones and markers of 5alpha-reductase activity are higher in Japanese compared with New Zealand males: what is the role of circulating steroids in prostate disease?

Epidemiological evidence implicates dietary isoflavone intake as protective against prostate disease. A putative mechanism is attenuated circulating androgen levels in male populations consuming an isoflavone rich diet. We investigated this hypothesis by collecting plasma from 60 Japanese and 60 New Zealand males aged between 21 and 31 years each consuming their traditional diets. We measured plasma testosterone, dihydrotestosterone (DHT), androstenedione, dehydroepiandrosterone sulfate (DHEAS), the combined levels of androsterone sulfate and epiandrosterone sulfate (AoS/epiAoS), sex hormone-binding globulin, and cortisol and corticosteroid-binding globulin as well as the isoflavones genistein and equol. Plasma genistein and equol levels were several times higher in Japanese males as would be expected from an isoflavone rich diet. However, androstenedione, DHEAS, calculated free testosterone and paradoxically markers of 5alpha-reductase, DHT and AoS/epiAoS were all also significantly higher in Japanese rather than the New Zealand male counterparts. All other comparisons were not significant. Plasma DHT and DHEAS correlated positively with plasma equol and plasma AoS/epiAoS correlated positively with genistein levels. Taken together the results suggest that, rather than reduced levels of steroidogenesis, Japanese males may have increased 5alpha-reductase activity and possibly altered 17beta OH steroid dehydrogenase activity. Significantly the positive association between isoflavones levels and 5alpha-steroids is counter-intuitive to isoflavone intake offering prostate protection, unless this is postulated to occur through other mechanisms.

Adult↗
PubMed2004

Plasma sex hormone-binding globulin rather than corticosteroid-binding globulin is a marker of insulin resistance in obese adult males.

AIM: Plasma levels of corticosteroid-binding globulin (CBG) and sex hormone-binding globulin (SHBG) may be regulated by insulin. The aim of this study was to test the hypothesis that these steroid-binding proteins are markers of insulin resistance and obesity in adult patients with the metabolic syndrome. METHODS: Fasting blood samples were obtained from 108 male and 88 female overweight adult patients who had varying degrees of dyslipidaemia, adiposity and insulin resistance. We measured plasma levels of SHBG and CBG and investigated their correlation with insulin resistance [homeostasis model assessment (HOMA) % sensitivity] and anthropometric markers of adiposity. RESULTS: In male patients, plasma SHBG correlated positively with HOMA (% sensitivity) and negatively with anthropometric measurements, including body mass index, waist circumference (cm) and percentage body fat. There was no correlation with CBG and any other parameter in the male patients. The female patients were treated as two groups, those not using oral contraceptives or hormone replacement therapy (n = 67) and those taking steroid medications (n = 21). Female patients using steroid medications had significantly higher SHBG levels but neither group showed any correlation between SHBG, insulin resistance and adiposity. Correlation studies of CBG with other parameters in the female subgroups did not reach statistical significance. CONCLUSIONS: We conclude that plasma SHBG is another surrogate marker for insulin resistance in obese males but not in obese females. It also appears that plasma CBG is not a useful marker of insulin resistance in patients with the metabolic syndrome.

Biomarkers↗
PubMed2000

Cadmium induces c-myc, p53, and c-jun expression in normal human prostate epithelial cells as a prelude to apoptosis.

Cadmium is a suspected human prostatic carcinogen shown to induce prostatic tumors and proliferative lesions in rats. The carcinogenic mechanism of cadmium is unknown, but its poor mutagenicity points toward an epigenetic mechanism. Here we studied the effect of cadmium on genes involved in growth regulation of prostate epithelial cell using the human prostate epithelial cell line RWPE-1, which is immortalized but not transformed and is androgen-responsive. Treatment with 10 microM cadmium resulted in transient increases in c-myc and p53 mRNA levels that peaked at 2-fold and 1.4-fold, respectively, compared to control after 2 h. In contrast, c-jun mRNA levels were increased >3-fold after 2, 4, and 6 h and 20-fold after 24 h. DNA synthesis decreased after 24 h of cadmium exposure. Further study revealed a significant increase in apoptosis after 48 h of cadmium exposure. However, approximately 35% of the cells were still viable and appeared normal, indicating this subpopulation was more resistant to cadmium. Furthermore, these resistant cells had 2.5-fold more metallothionein than untreated control cells. This suggests that cadmium could act to select for apoptotic-defective cells in vivo, thereby increasing the likelihood of tumor formation. This work represents the first description of cadmium affecting oncogene expression in a human cell model of a potential in vivo target site of cadmium carcinogenesis.

Apoptosis↗
PubMed1999

Exposure of cultured murine peritoneal macrophages to low concentrations of beryllium induces increases in intracellular calcium concentrations and stimulates DNA synthesis.

Exposure of humans to beryllium dusts can induce a specific form of chronic pneumonitis that consists mainly of noncaseating granulomas in the lungs. Multiple studies have documented both genetic and immune components of chronic berylliosis. Much work has focused on T cells and their reactivity in berylliosis, but less work has focused on the end effector cells in granulomatous inflammation, macrophages. Because macrophages must become activated to form granulomas, and they become activated by responding to numerous immunomodulatory signals, we investigated the effects of beryllium (BeCl2) on a central signal transduction pathway in macrophages, increases in intracellular calcium ([Ca2+]i). Exposure of cultured murine peritoneal macrophages to low, nontoxic concentrations induced successive spikes or oscillations in [Ca2+]i. Concentrations as low as 5 nM induced significant increases in [Ca2+]i. The source of the increased [Ca2+]i was exclusively extracellular in that increases in [Ca2+]i could be completely blocked by chelating extracellular Ca2+, were inhibited by the Ca2+ channel blocker verapamil, and exposure of macrophages to BeCl2 had no effect on IP3 concentrations. DNA synthesis, a Ca2+-sensitive function, was enhanced in dividing 1LN cells and induced de novo in quiescent macrophages. Furthermore, BeCl2 enhanced DNA synthesis in the absence of coexposure to the protein kinase C activator phorbol myristate acetate. These data support the hypothesis that beryllium toxicity is in part the result of altered Ca2+ metabolism in mononuclear phagocytes consequent to reversible opening of plasma membrane channels.

Animals↗
PubMed1999

Monoclonal antibodies to human sex hormone-binding globulin (SHBG): characterization and use in a simple enzyme-linked immunosorbent assay (ELISA) of SHBG in plasma.

Four monoclonal antibodies to human sex hormone-binding globulin were raised and characterized. Three of the four antibodies recognised different antigenic determinants on SHBG. Two of the distinct antibodies were useful for Western blotting and recognized a major 48 kDa band in human plasma as well as a 46 kDa minor component. Carbohydrate residues do not form part of the antigenic determinants of these two antibodies, although one of these showed increased signal following removal of N-linked oligosaccharides. Some of the antibodies were selected to form a basis of a same-day, non-competitive, enzyme-linked immunosorbent assay (ELISA) for SHBG in plasma. The assay employs a purified IgG2a SHBG monoclonal antibody adsorbed to the wells of a microtitre plate. After blocking any further adsorption to the plate, standards or diluted patient samples were added for a 5-h incubation at room temperature, after which the plate was washed and antibody-bound SHBG was detected with an anti-SHBG IgG1 monoclonal antibody followed by peroxidase-labeled antimouse-IgG1 and o-phenylenediamine substrate. The assay correlated well with an existing 2-day ELISA for SHBG in plasma using polyclonal antibodies and also correlated with a dihydrosterone (DHT) ligand-binding assay. The monoclonal antibody-based ELISA shows excellent performance characteristics and is unaffected by added testosterone or estradiol.

Adult↗
PubMed1999

Wellens' syndrome.

We describe a patient with Wellens' syndrome. In view of the large area of myocardium at risk, the importance of recognizing the significance of this ECG pattern is of critical importance for the emergency physician, especially those involved in the evaluation of patients at emergency department chest pain centers. Wellens' syndrome, the criteria for diagnosis, and a discussion of its implications are presented.

Adult↗
PubMed1999

Exposure of C57BL/6 mice to carbon disulfide induces early lesions of atherosclerosis and enhances arterial fatty deposits induced by a high fat diet.

Even though atherosclerotic cardiovascular disease (ACVD) is the number one cause of death in the United States, the effects of environmental toxicants on this process are less well studied than the effects of chemicals on the second leading cause of death, cancer. There is considerable epidemiological evidence that workers exposed to carbon disulfide (CS2) have increased rates of ACVD, and there is conflicting evidence of the atherogenic potential of CS2 from animal studies. Chemical modification, such as oxidation of low-density lipoproteins (LDL), is tightly associated with increased LDL uptake by macrophages and the development of arterial fatty streaks. CS2 has been previously demonstrated to modify several proteins in vitro including LDL, and others in vivo through derivatization and covalent cross-linking. To investigate both the capacity of CS2 to induce arterial fatty deposits by itself, and its ability to enhance the rate of fatty deposit formation induced by a western style, high fat diet, groups of 20 female C57BL/6 mice were exposed to 0, 50, 500, or 800 ppm CS2 by inhalation. Half the animals in each group were placed on an atherogenic high fat diet and half on a control diet (NIH-07). Animals were sacrificed after 1, 4, 8, 12, 16, or 20 weeks of exposure, and the rates of fatty deposit formation under the aortic valve leaflets were evaluated. Exposure of mice on the control diet to 500 and 800 ppm CS2 induced a small but significant increase in the rate of fatty deposit formation over non-exposed controls. A more striking result was observed in the animals on the high fat diet. There was marked enhancement of the rate of fatty deposit formation in mice exposed to 500 and 800 ppm over the animals on the high fat diet alone. In addition, there was a small but significant enhancement in mice exposed to 50 ppm over the rate of fatty deposit formation induced by the high fat diet alone. Analysis of erythrocyte spectrin for protein cross-linking revealed a dose-dependent formation of alpha- and beta-heterodimers in animals on both diets. These data demonstrate that CS2 is atherogenic at high concentrations, but more importantly, suggest that, in conjunction with other risk factors, CS2 at relatively low concentrations can enhance atherogenesis.

Administration, Inhalation↗
PubMed1998

Alterations in calcium metabolism in murine macrophages by the benzene metabolite 1,4-benzoquinone.

Exposure of murine peritoneal macrophages to very low concentrations of 1,4-benzoquinone (BQ) induced immediate increases in intracellular Ca2+ concentrations ([Ca2+]i). Increases in [Ca2+]i were induced by concentrations as low as 5 nM and the response was dose dependent and linear up to 1 microM. The sources of Ca2+ were from both internal inositol triphosphate (IP3)-sensitive and -insensitive sites and from the external medium. BQ did not induce IP3 formation and did not affect binding to its receptors. 1, 4-Hydroquinone had no effect on [Ca2+]i. Catechol did elicit some increases in [Ca2+]i, but did so only at much higher concentrations (5 microM). The action of BQ was almost identical to that of the established Ca2+-ATPase inhibitor thapsigargin except that there were some intracellular stores of Ca2+ released by thapsigargin that were not released by BQ. BQ also was mitogenic for macrophages in conjunction with phorbol myristate acetate. These data suggest that BQ raises [Ca2+]i by inhibition of Ca2+-ATPases, is a comitogen, and does so at concentrations that could be achieved in vivo in the general urban population.

Animals↗
PubMed1997

Stress co-tolerance and trehalose content in baking strains of Saccharomyces cerevisiae.

Fourteen wild-type baking strains of Saccharomyces cerevisiae were grown in batch culture to true stationary phase (exogenous carbon source exhausted) and tested for their trehalose content and their tolerance to heat (52 degrees C for 4.5 min), ethanol (20% v/v for 30 min), H2O2 (0.3 M for 60 min), rapid freezing (-196 degrees C for 20 min, cooling rate 200 degrees C min-1), slow freezing (-20 degrees C for 24 h, cooling rate 3 degrees C min(-1)), salt (growth in 1.5 M NaCl agar) or acetic acid (growth in 0.4% w/v acetic acid agar) stresses. Stress tolerance among the strains was highly variable and up to 1000-fold differences existed between strains for some types of stress. Compared with previously published reports, all strains were tolerant to H2O2 stress. Correlation analysis of stress tolerance results demonstrated relationships between tolerance to H2O2 and tolerance to all stresses except ethanol. This may imply that oxidative processes are associated with a wide variety of cellular stresses and also indicate that the general robustness associated with industrial yeast may be a result of their oxidative stress tolerance. In addition, H2O2 tolerance might be a suitable marker for the general assessment of stress tolerance in yeast strains. Trehalose content failed to correlate with tolerance to any stress except acetic acid. This may indicate that the contribution of trehalose to tolerance to other stresses is either small or inconsistent and that trehalose may not be used as a general predictor of stress tolerance in true stationary phase yeast.

Acetic Acid↗
PubMed1997

Differential responsivity of monocyte cytokine and adhesion proteins in high- and low-hostile humans.

This study tested the general hypothesis that high- and low-hostile respondents would show different patterns of change in monocyte cytokine and adhesion protein (MCAP) expression in response to pharmacologically induced alterations in sympathetic nervous system (SNS) and parasympathetic nervous system (PNS) balance. On 3 separate days, 4 high- and 4 low-hostile respondents received isoproterenol infusions after saline, atropine (PNS blockade), or neostigmine (PNS stimulation) pre-treatment. Dual color flow cytometry with fluorescently labeled monoclonal antibodies to CD 14 (monocyte market), interleukin-1, leukocyte function activator (LFA-1), Class II major histocompatibility complex (MHC-II), and tumor necrosis factor was used to quantify cytokine and adhesion protein expression on monocytes in blood samples drawn before and after the combination drug infusions on the 3 test days in each respondents. Following PNS stimulation and istoproterenol infusion there was a decrease (compared to saline pretreatment) in MHC II expression in high hostiles that was significantly (p<.02) different from an increase in low hostiles. A similar trend (p = .08) was seen for LFA-1 expression, with high hostiles showing an increase and low hostiles a decrease. These findings support the broad hypothesis that high-and low-hostile respondents will show different MCAP responses to pharmacologically induced alterations in SNS-PNS balance. Such differences could contribute to accelerated atherogenesis among high-hostile individuals.

Journal Article↗
PubMed1996

A serum-resistant cytofectin for cellular delivery of antisense oligodeoxynucleotides and plasmid DNA.

Development of antisense technology has focused in part on creating improved methods for delivering oligodeoxynucleotides (ODNs) to cells. In this report, we describe a cationic lipid that, when formulated with the fusogenic lipid dioleoylphosphatidyliethanolamine, greatly improves the cellular uptake properties of antisense ODNs, as well as plasmid DNA. This lipid formulation, termed GS 2888 cytofectin, (i) efficiently transfects ODNs and plasmids into many cell types in the presence or absence of 10% serum in the medium, (ii) uses a 4- to 10-fold lower concentration of the agent as compared to the commercially available Lipofectin liposome, and (iii) is > or = 20-fold more effective at eliciting antisense effects in the presence of serum when compared to Lipofectin. Here we show antisense effects using GS 2888 cytofectin together with C-5 propynyl pyrimidine phosphorothioate ODNs in which we achieve inhibition of gene expression using low nanomolar concentrations of ODN. This agent expands the utility of antisense ODNs for their use in understanding gene function and offers the potential for its use in DNA delivery applications in vivo.

Base Sequence↗