Static and dynamic behaviour of responsive graphene oxide-poly(N-isopropyl acrylamide) composite gels.

Thermoresponsive hydrogels have enormous potential e.g., as sensors, actuators, and pollution control remedies or in drug delivery systems. Nevertheless, their application is often restricted by physical limitations (poor mechanical strength and uncontrolled thermal response). Composite systems may offer a means of overcoming these limitations. This paper presents a systematic study of the structure and dynamics of graphene oxide-poly-(N-isopropylacrylamide) composite systems, and investigates the effect of the nanoparticle filler content on the mechanical and swelling properties of the systems. A combination of macroscopic (swelling and elastic modulus) and microscopic (differential scanning microcalorimetry, small angle neutron scattering and neutron spin-echo spectroscopy) investigations reveals that the architecture of the polymer network is modified by chain nucleation at the surface of the GO platelets, and these form a percolating network inside the gel. Our results show that the elastic modulus of the gels is reinforced by the filler, but the mobility of the polymer chains in the swollen state is practically unaffected. The macroscopic deswelling of the composites, however, is slowed by the kinetics of ordering in the GO network.

Sub-cellular Ca2+ dynamics affected by voltage- and Ca2+-gated K+ channels: Regulation of the soma-growth cone disparity and the quiescent state in Drosophila neurons.

Using Drosophila mutants and pharmacological blockers, we provide the first evidence that distinct types of K(+) channels differentially influence sub-cellular Ca(2+) regulation and growth cone morphology during neuronal development. Fura-2-based imaging revealed in cultured embryonic neurons that the loss of either voltage-gated, inactivating Shaker channels or Ca(2+)-gated Slowpoke BK channels led to robust spontaneous Ca(2+) transients that preferentially occurred within the growth cone. In contrast, loss of voltage-gated, non-inactivating Shab channels did not show such a disparity and sometimes produced soma-specific Ca(2+) transients. The fast spontaneous transients in both the soma and growth cone were suppressed by the Na(+) channel blocker tetrodotoxin, indicating that these Ca(2+) fluctuations stemmed from increases in membrane excitability. Similar differences in regional Ca(2+) regulation were observed upon membrane depolarization by high K(+)-containing saline. In particular, Shaker and slowpoke mutations enhanced the size and dynamics of the depolarization-induced Ca(2+) increase in the growth cone. In contrast, Shab mutations greatly prolonged the Ca(2+) increase in the soma. Differential effects of these excitability mutations on neuronal development were indicated by their distinct alterations in growth cone morphology. Loss of Shaker currents increased the size of lamellipodia and the number of filopodia, structures associated with the actin cytoskeleton. Interestingly, loss of Slowpoke currents strongly influenced tubulin regulation, enhancing the number of microtubule loop structures per growth cone. Together, our findings support the idea that individual K(+) channel subunits differentially regulate spontaneous sub-cellular Ca(2+) fluctuations in growing neurons that may influence activity-dependent growth cone formation.

Dietary antioxidants, peroxidation and cardiovascular risks.

Most of the many epidemiological studies in the field strongly suggest that an equilibrated diet such as the so-called "mediterranean diet", is associated with protective effects against major diseases, and particularly, against cardiovascular risks. Since many reports also consider reactive oxygen species or free radical oxidations to be responsible for the accompanying disorders of most pathologies as well as for ageing, it is conceivable that natural plant metabolites such as polyphenols, are likely to play an important role in insuring this protection. Indeed, not only their presence, in particularly high amounts and varieties in foods of such a diet, but also, inter alia, their very potent antioxidant or radical scavenging properties, make polyphenols best accounting for the parodoxical part of the french paradox . Therefore, many efforts have been made to assess the mechanisms for such a cardiovascular disease protection. Whatever convincing were the polyphenols properties demonstrated by many in vitro experiments to support those theories, quite a great number of the results appeared somewhat contradictory when transposed to humans, in the in vivo situation. Some people totally refute this explanation, thinking that health benefits, as far as alcoholic beverages are concerned, originate from ethanol but also, with no doubt, some polyphenols even revealing to be pro-oxidants .

NMR and simulated annealing investigations of bradykinin in presence of polyphenols.

Epidemiological studies have shown that the incidence of some cardiovascular degenerative diseases appears to be lower in populations with regular but moderate drinking of red wine rich in polyphenols. One of the most important properties of polyphenols is to form complexes with proteins. The linear nonapeptide hormone bradykinin (H-Arg1-Pro2-Pro3-Gly4-Phe5-Ser6-Pro7-Phe8-Arg9-OH) is involved in a variety of physiological processes such as the cardiovascular processes. Thus, the goal of this work was to study the effects of tannins on the peptide structure by NMR investigations and molecular modeling. The results of these investigations show that in the presence of catechin, the peptide conformation is not affected and is in a random coil structure. On the contrary, the peptide structure is modified by the addition of dimeric proanthocyanidin B3 (catechin 4alpha-->8 catechin). The dimer leads to the formation of a large flexible turn between the 6-9 residues. Thus, the biological activities of bradykinin in the presence of polyphenols could be affected.

DNA triplex stabilization property of natural anthocyanins.

The DNA triplex stabilization property of seven natural anthocyanins (five monoglucosides and two diglucosides) has been measured by the mean of triplex thermal denaturation experiments. We have noticed a difference between the diglucosides that do not modify this melting temperature and the monoglucosides (namely 3-O-beta-D-glucopyranoside of malvidin, peonidin, delphinidin, petunidin and cyanidin) which present a weak but significant stabilizing effect. It appears clearly that the difference between the two series could be due to the supplementary sugar moiety at the 5 position for the diglucosylated compounds, that would make them too crowded to allow interaction with the triplex. Among the monoglucoside series, the most active compounds are the only ones to embody a catechol B-ring in their structure that could be important for such an interaction. The need to have pure and fully characterized compounds to run these measurements, made it possible for us to unambiguously assign the 1H and 13C NMR spectra with the help of 2D NMR experiments. Thus, missing data of compounds not totally described earlier, are provided herein.

Atrial natriuretic peptide alters neither capillary filtration nor vascular compliance of both skin and skeletal muscle of humans.

We studied the effects of hANP 99-126 on capillary filtration and venous compliance in both the calf (mainly skeletal muscle) and foot (mainly skin) of humans. Six healthy mean received ANP (intravenous injection of 25 micrograms followed by continuous infusion of 0.1 microgram.kg-1.min-1) for 30 min. Another six men served as time controls. Capillary filtration coefficient, venous compliance, and also volume and blood flow of both calf and foot were measured repeatedly by occlusion plethysmography before, during, and after ANP. Additionally, we determined hematocrit, central venous pressure, venous pressure in the foot, arterial pressure, and heart rate. Filtration coefficients, venous compliance, blood flow of both calf and foot as well as arterial blood pressure did not change systematically during the infusion of ANP, and yet leg volume and central venous pressure (3.1 +/- 0.8 cm H2O) decreased while both hematocrit (3.1 +/- 1.0%) and heart rate (17 +/- 11 min-1) increased. Thus, the ANP-evoked decrease in central venous pressure and increase in hematocrit are unrelated to blood pooling or increases in capillary filtration in skeletal muscle and skin of healthy humans.

Elevated TNF receptor plasma concentrations in patients with rheumatoid arthritis.

Two types of tumor necrosis factor receptors have been characterized, both capable of transmitting the signal and exerting the biological functions of TNF and lymphotoxin. We measured the plasma concentrations of two types of TNF binding proteins (sTNFR-A and sTNFR-B) in patients with rheumatoid arthritis (RA) and spondylarthropathies (SpA) using an enzyme-linked binding assay. In normal controls (n = 43), mean plasma concentrations were 1030 +/- 55 and 1461 +/- 59 pg/ml for sTNFR types A and B, respectively. In 67 patients with moderate RA, mean levels were 1422 +/- 82 pg/ml (type A) and 2088 +/- 109 pg/ml (type B); in 34 patients with severe RA, 2588 +/- 279 pg/ml and 4494 +/- 550 pg/ml, respectively, were measured (P less than 0.0001 compared to normal controls). Concentrations of both type A and type B sTNFR were highly correlated in severe RA (R2 = 0.7) but not in SpA or normal controls. T lymphocytes in synovial fluid of patients with RA expressed predominantly type A TNF receptors on their surface; in some patients a weaker expression of type B receptors was also detectable. Soluble TNF binding proteins in patients with RA were able to neutralize TNF in a cytotoxicity assay, demonstrating their ability to act as "TNF-inhibiting factors". We conclude that both types of TNF receptors are parameters of disease activity in RA and may also act as TNF antagonists.

Serum prolactin and growth hormone determined by radioimmunoassay and a two-site immunoradiometric assay: comparison with the Nb2 cell bioassay.

Serum levels of the two lactogenic hormones prolactin (PRL) and growth hormone (GH) were compared when determined by radioimmunoassay (RIA) and two-site immunoradiometric (IRMA) assays in 83 normal premenopausal women. The mean values for the PRL and GH results determined by RIA were higher than those obtained by IRMA, despite strong correlations between the two (PRL, r = 0.92; GH, r = 0.79). The lactogenic hormones were also determined together by the Nb2 cell bioassay (BA) in 38 of these same women, and the results compared with the sum of the PRL and GH immunoassays. There was a strong correlation between the BA and RIA (r = 0.75), and the BA/PRL+GH RIA ratio averaged 1.6 +/- 0.5. Corresponding values for IRMA were r = 0.66, and BA/PRL + GH IRMA 3.3 +/- 1.1. Thus, the polyclonal RIA antisera appeared to recognize bioactive hormone components not determined by the double monoclonal antibody IRMA. Another 23 women at risk for familial breast cancer, and 14 cystic breast disease patients were also studied. High BA, but normal RIA results, giving mean ratios of 2.4 +/- 1.1 and 3.6 +/- 3.0 respectively, suggest the presence of a further variant with high bioactivity not detected by RIA in these two clinical situations.

A comparison of serum and breast duct fluid-immunoassayable prolactin and growth hormone with bioassayable lactogenic hormones in healthy women and patients with cystic breast disease.

Serum and breast fluid obtained by nipple aspiration were collected from 46 healthy premenopausal women, and 36 patients with cystic breast disease and cyclical mastalgia of similar age. Serum prolactin and growth hormone levels determined by radioimmunoassay were similar in the two groups, but the patients showed a significant elevation in bioactive lactogenic hormones (prolactin plus growth hormone) as determined by the Nb2 rat lymphoma cell bioassay (P less than 0.001). The radioimmunoassayable prolactin levels in breast fluid were extremely variable; there was a trend towards higher concentrations in the cystic breast disease patients, but this just failed to achieve statistical significance (P = 0.06). Immunoreactive growth hormone was rarely detected in nipple aspirates obtained from either the patient or control groups. The mean breast fluid bioactive lactogenic hormone level was significantly higher in the cystic breast disease patients than in the normal controls (P less than 0.001); also ten of 46 (22%) controls, but only two of 36 (6%) patients had no detectable bioactivity. It is concluded that lactogenic hormone bioactivity, when assessed by the Nb2 cell assay, is indicative of an endocrine abnormality which is associated with benign breast disease, and is reflected in breast duct fluid, but is not identified by the conventional radioimmunoassays.

Effect of a low-fat diet on hormone levels in women with cystic breast disease. II. Serum radioimmunoassayable prolactin and growth hormone and bioactive lactogenic hormones.

For investigation of the bioactivity of circulating prolactin and growth hormone (lactogenic hormones) in symptomatic benign breast disease, serum was assayed by the Nb2 lymphoma cell method in premenopausal patients with cystic breast disease and cyclic mastalgia and in normal premenopausal women. The results were compared with serum prolactin and growth hormone concentrations determined by radioimmunoassay. The serum bioassayable hormone levels in the benign breast disease patients (74.0 +/- 77.6 ng/ml) were significantly higher (P less than .001) than in normal women (23.8 +/- 10.7 ng/ml). There were no significant differences in the radioimmunoassayable prolactin or growth hormone levels between the 2 groups. When 16 cystic breast disease patients were placed on a low-fat (20% of total kilocalories) diet for 3 months, there were significant reductions in the serum bioassayable hormone levels (P less than .02). It is concluded that the bioactivity of prolactin may be elevated in the serum of patients with cystic breast disease and cyclic mastalgia, without corresponding increases in levels determined by radioimmunoassay; that this abnormality is reversible by a reduction in dietary fat consumption to 20% of the total kilocalories; and that serum prolactin may provide a valuable biomarker in clinical trials of a low-fat diet in women at high breast cancer risk.

Inhibition of chemically induced mammary carcinogenesis in rats by long-term exposure to butylated hydroxytoluene (BHT): interrelations among BHT concentration, carcinogen dose, and diet.

In outbred female Sprague-Dawley rats long-term exposure to dietary butylated hydroxytoluene [3,5-di-tert-butyl-4-hydroxytoluene (BHT); CAS: 128-37-0] 1 week before carcinogen administration to termination resulted in a dose-related inhibition of mammary tumorigenesis and adrenocortical nodulogenesis. In animals fed the cereal-based NIH-07 diet and receiving a low dose (5 mg/rat) of 7,12-dimethylbenz [a] anthracene [(DBMA) CAS: 57-97-6], there was a significant overall inhibitory trend in tumor incidence observed among those receiving 300, 1,000, 3,000, and 6,000 ppm BHT. Maximal inhibition was approximately 50% at the highest concentration of BHT (6,000 ppm). The inhibitory effect of BHT on mammary tumor incidence was less pronounced when BHT was administered to rats initiated with a high carcinogen dose: At 15 mg DMBA/rat maximal inhibition was only 20% at the highest concentration of BHT (6,000 ppm). In contrast, when tumor yield was assessed in terms of latency or tumor multiplicity, the inhibitory effect of BHT was more pronounced in the groups given a high dose of DMBA than in the groups given a low dose. In animals given a low dose of DMBA (5 mg) and fed 6,000 ppm BHT in the casein-based AIN-76A diet, tumor incidence was inhibited by 50% of that of the controls; in contrast, when initiation was with a high dose of DMBA (15 mg), tumor incidence was decreased by only 28% of that of the controls. In animals fed the NIH-07 diet, DMBA-induced adrenocortical nodule formation was also inhibited in a dose-dependent fashion by BHT. At 5 mg DMBA maximal inhibition was 86% of control levels (6,000 ppm BHT); at 15 mg DMBA maximal inhibition was 66% of control levels (6,000 ppm BHT). However, when BHT was incorporated into the AIN-76A diet, its inhibitory effects on adrenocortical nodulogenesis were unexpectedly feeble and unrelated to carcinogen dose: In animals initiated with 5 mg DMBA and administered 6,000 ppm BHT, nodule incidence was decreased by only 25%, whereas in animals initiated with 15 mg DMBA, nodule incidence was decreased by 30% of that of the controls. These results indicate that while chronic exposure to dietary BHT suppressed the development of DMBA-induced mammary tumors and adrenocortical nodules, the degree of suppression depended on the dose of carcinogen administered, the level of BHT in the diet, and the parameter being measured. Diet-dependent differences in BHT action were observed with regard to DMBA-induced adrenocortical nodulogenesis but not with regard to mammary tumorigenesis.

Inhibition of chemically induced mammary carcinogenesis in rats by short-term exposure to butylated hydroxytoluene (BHT): interrelationships among BHT concentration, carcinogen dose, and diet.

Dietary butylated hydroxytoluene (BHT) fed 14 days before and 14 days after carcinogen administration resulted in a dose-dependent inhibition of 7, 12-dimethylbenz[a]anthracene (DMBA)-induced mammary tumor incidence in outbred Sprague-Dawley rats. In addition, the inhibitory effects of BHT were strongly influenced by the dose of initiating carcinogen and the type of diet in which BHT was administered. In animals fed the NIH-07 diet and receiving a low dose of DMBA (5 mg/rat), the inhibitory effect of BHT was manifested at all four BHT concentrations (6,000 leads to 300 ppm). Maximal inhibition was approximately 50% in animals given 5 mg DMBA and receiving 6,000 ppm BHT. However, in the group administered a high dose of DMBA (15 mg/rat), the inhibitory effect of BHT was expressed only at 6,000 ppm, the highest concentration given. Lower concentrations (300 and 1,000 ppm) of BHT had no detectable effect on tumor incidence. In animals fed the defined, semipurified AIN-76A diet during the 4-week treatment period and initiated with 5 mg DMBA, BHT at 6,000 ppm inhibited tumor development. However, at 15 mg DMBA animals fed the AIN-76A diet differed markedly from those fed the NIH-07 diet. In the former group, BHT at 6,000 ppm was unable to elicit any inhibitory response; in the latter group, BHT inhibited tumor development by 40%. Dietary BHT also inhibited DMBA-induced adrenocortical hyperplastic nodules in a dose-dependent fashion. These results indicate that short-term exposure to dietary BHT can inhibit experimental mammary tumor development at environmentally relevant concentrations.

Effects of high fat and high carbohydrate diets on development of hepatic and adipose lipogenesis in fa/fa and non-fa/fa rats.

Non-fa/fa and fa/fa rats were weaned at 18 days of age and fed either a high fat or high carbohydrate diet. At 6 weeks of age some of the rats fed high fat were fed the high carbohydrate diet until 10 weeks of age. Food consumption was equalized between all treatment groups. Epididymal fat pads were heavier in the fa/fa rats in all treatment groups. Fat pad weight and cellularity increased in the non-fa/fa rats fed the high fat diet. Cellularity was actually less in the fa/fa than in the non-fa/fa rats, but high fat feeding resulted in higher proportions of larger adipocytes in both phenotypes. Rates of epididymal fat pad lipogenesis and enzymatic activities were similar in both non-fa/fa and fa/fa rats in all treatment groups. Hepatic fatty acid synthesis and enzymatic activities were consistently greater in the fa/fa rats. Carbohydrate feeding resulted in increased hepatic fatty acid synthesis regardless of the earlier feeding of the fat diet, but the fa/fa rats were more responsive to the carbohydrate diet than the non-fa/fa rats. A delay in introduction of carbohydrate to the diet did not alter the eventual lipogenic capacity of fa/fa rats. Lipogenesis appeared responsive to the most recent diet.

Effect of dietary butylated hydroxyanisole on methylazoxymethanol acetate-induced toxicity in mice.

Administration of butylated hydroxyanisole (BHA), a widely used food additive, has been found to inhibit the carcinogenic and toxic effects of various chemicals in animal models. To study the relationship of dietary BHA to the acute toxicity of methylazoxymethanol (MAM) acetate, a colon-specific carcinogenic compound, groups of female CF1 mice were fed NIN-07 diet containing 0, 300, 1000, 3000 or 6000 ppm BHA or a semipurified diet containing 0 or 6000 ppm BHA for 4 wk, and were injected ip with MAM acetate (20 mg/kg body weight) at the end of the first 2 wk and again 4 days later. At levels of 300-6000 ppm, BHA was found to protect against death caused by MAM acetate. The mortality rates in MAM-treated mice were 80 and 92% in those fed the diets with no BHA and 0 and 1% in those fed 6000 ppm BHA, and were inversely related to the amount of BHA in the diet. The protection was associated with increased levels of hepatic cytochrome P-450 and b5 and with a reduction in necrotic changes in the liver.

Tumor-associated lymphoid cells: analysis of host cells that bind to syngeneic and allogeneic tumor cells shortly after tumor administration.

A single intraperitoneal injection of irradiated EL-4 leukemia into syngeneic hosts induced in vivo immunity and in vitro cell-mediated response against EL-4. A nonadherent, theta-positive, peritoneal exudate lymphocyte fraction that bound to and lysed EL-4 in vitro was isolated from the tumor site. This system allowed the study of immune processes involving host lymphocytes as early as 3 days after tumor inoculation.