Development of a reactor for the in situ monitoring of 2D materials growth on liquid metal catalysts, using synchrotron x-ray scattering, Raman spectroscopy, and optical microscopy.

Liquid metal catalysts (LMCats) (e.g., molten copper) can provide a new mass-production method for two-dimensional materials (2DMs) (e.g., graphene) with significantly higher quality and speed and lower energy and material consumption. To reach such technological excellence, the physicochemical properties of LMCats and the growth mechanisms of 2DMs on LMCats should be investigated. Here, we report the development of a chemical vapor deposition (CVD) reactor which allows the investigation of ongoing chemical reactions on the surface of a molten metal at elevated temperatures and under reactive conditions. The surface of the molten metal is monitored simultaneously using synchrotron x-ray scattering, Raman spectroscopy, and optical microscopy, thereby providing complementary information about the atomic structure and chemical state of the surface. To enable in situ characterization on a molten substrate at high temperatures (e.g., ∼1370 K for copper), the optical and x-ray windows need to be protected from the evaporating LMCat, reaction products, and intense heat. This has been achieved by creating specific gas-flow patterns inside the reactor. The optimized design of the reactor has been achieved using multiphysics COMSOL simulations, which take into account the heat transfer, fluid dynamics, and transport of LMCat vapor inside the reactor. The setup has been successfully tested and is currently used to investigate the CVD growth of graphene on the surface of molten copper under pressures ranging from medium vacuum up to atmospheric pressure.

Effects of dietary calcium content and vitamin D source on skeletal properties in growing turkeys.

1. The aim of the study was to investigate the effects of feeding fast growing turkeys with differentiated dietary calcium (Ca) content, and the partial replacement of vitamin D(3) in the feed with 25-hydroxycholecalciferol (25(OH)D(3)), on skeletal properties. 2. One-day-old Big-6 male turkeys (n = 1008) were randomly divided into 4 groups, and two subgroups were created within each group. The groups were differentiated with 4 levels of Ca provision in the feed, namely 85% of the National Research Council (NRC) recommendation (Group Ca(1)); 95% as above (Group Ca(2)); 105% as above (Group Ca(3)); and 115% as above (Group Ca(4)). The first subgroup received the recommended dosage of cholecalciferol (vitamin D(3) subgroup) in the feed, while in the second subgroup (Hy-D subgroup), half of the dosage of cholecalciferol was replaced with 25(OH)D(3). At the ages of 4, 8, 12 and 20 weeks, 7 turkeys from each subgroup were randomly selected and killed to obtain the right tibia for densitometric, geometric and mechanical analyses. 3. This study showed advantageous effects of increased calcium supply in the diet on skeletal system properties, that were increased and produced the most desirable traits in turkeys receiving 95%, 105% and 115% of the NRC calcium recommendation. Benefits resulting from administration of 25(OH)D(3) in the diet were also obtained in the skeletal formation of turkeys, and the most advantageous effects were present in the group receiving 105% of recommended dietary Ca. 4. Effects on the metabolic response of the skeleton of turkeys to manipulation of dietary calcium content and vitamin D(3) source were the most evident in the groups between 4 and 12 weeks of life, and demonstrated a limited ability to induce a positive influence on bone properties at advanced stages of the production cycle by alteration of these dietary factors.

Changes of atrial natriuretic peptide in rat supraoptic neurones during pregnancy.

To better understand the role of atrial natriuretic peptide (ANP) in the central regulation of hydro-mineral homeostasis, we analysed its expression in rat hypothalamic neurones during gestation and postpartum. These physiological events are characterized by opposing body fluid regulations. Quantitative in situ hybridization analysis showed that starting from mid-pregnancy, ANP mRNA declined in neurones of the preoptic area, periventricular area, lateral hypothalamus and endorhinal nucleus, and remained low at postpartum. By contrast, magnocellular cells in the supraoptic nucleus (SON) showed four- and 10-fold more ANP mRNA in sections from preterm and postpartum rats, respectively, compared to nonpregnant controls (P < 0.001). Oxytocin mRNA paralleled ANP mRNA expression in the SON, whereas vasopressin mRNA rose in early pregnancy and declined thereafter. High hypothalamic ANP concentration at day 21 of gestation versus nonpregnant rats (3.1 +/- 0.5 versus 1.8 +/- 0.4 ng/mg protein, P < 0.05) suggested that ANP transcript accumulation in the SON is associated with increased utilization of the peptide. The elevation of hypothalamic ANP (two-fold) and ANP receptors by treatment of ovariectomized rats with 17beta-oestradiol (25 micro g/rat, 10 days) was abolished by coadministration of progesterone. Thus, we concluded that elevated oestradiol at term stimulates ANP synthesis and paracrine ANP activation in the hypothalamus. Overall, we provide experimental, anatomical and molecular evidence for ANP regulation in hypothalamic neurones at preterm and after 17beta-oestradiol stimulation. Our study supports the concept that ANP expressed in the SON acts as a peptidergic neurotransmitter involved in water and salt regulation during pregnancy and postpartum.

Rat embryos cultured under copper-deficient conditions develop abnormally and are characterized by an impaired oxidant defense system.

Rat embryos (gestation days 9.0 and 10.0) obtained from dams that were fed a Cu-adequate (8 micrograms Cu/g) or Cu-deficient (< 0.5 micrograms Cu/g diet were cultured for 48 hr in Cu-adequate (16.2 microM) or Cu-deficient (1.0 microM) rat serum. Control embryos cultured in control serum were morphologically normal. Embryos from Cu-deficient dams developed abnormally when cultured in Cu-deficient serum; the abnormalities included distended hindbrains, blisters, blood pooling, and cardiac defects. Control embryos cultured in Cu-deficient serum and Cu-deficient embryos cultured in control serum also showed abnormal development, but to a lesser degree than that of the Cu-deficient embryos cultured in Cu-deficient serum. To test the idea that the above abnormalities were due in part to free radical induced damage occurring secondary to an impaired oxidant defense system, a chemiluminescence assay was used to detect superoxide dismutase (SOD) activity in the cultured embryos. SOD activity was lowest in embryos cultured in Cu-deficient serum. When the Cu-deficient serum was supplemented with antioxidants (CuZnSOD or glutathione peroxidase), its teratogenicity was reduced. These data support the idea that an impaired oxidant defense system contributes to the dysmorphology associated with Cu deficiency. However, the Cu-deficient embryos also had low cytochrome c oxidase activity compared to control embryos--thus, multiple factors are likely contributing to Cu deficiency-induced abnormalities.

Natriuretic peptide system in the rat submaxillary gland.

Natriuretic peptides and their receptors were characterized in rat submaxillary glands (SGs). Reverse phase-high performance liquid chromatography (HPLC) of rat SGs extracts revealed the presence of the 28-amino-acid (AA) circulating peptide ANP (Ser99-Tyr126) and the 126-AA prohormone (Asn1-Tyr126). The presence of ANP prohormone indicated that SGs are a site of ANP synthesis. Indeed, ANP mRNAs were demonstrated. ANP mRNA was 10 times lower than in the lung and only about 7 times lower than in the hypothalamus. ANP content in SG was determined as 30 +/- 8 ng/mg of protein (n = 7). In addition the presence of another member of the natriuretic peptide family, C-type natriuretic peptide (CNP), was found in SG. The CNP level of 293 +/- 38 pg/mg protein was significantly higher than in the lungs (44 +/- 6 pg/mg protein, P < 0.001, n = 5), but about 15 times lower than in hypothalamus (4.5 +/- 0.6 ng/mg protein, P < 0.001, n = 6). Both guanylyl cyclase and clearance receptors were expressed in SG. The presence of natriuretic peptide transcripts and their receptors suggests a role in rat SG functions.

Maternal zinc deficiency, but not copper deficiency or diabetes, results in increased embryonic cell death in the rat: implications for mechanisms underlying abnormal development.

The mechanisms underlying the teratogenicity of maternal copper deficiency, zinc deficiency, and diabetes are largely unknown. Here we investigated whether these insults are associated with altered patterns of cell death in gestation day (GD) 11.0 rat embryos. Four weeks prior to mating, rats in the copper-deficient group (CuD) were fed a copper-deficient diet supplemented with the chelator, triethylenetetramine, to facilitate the depletion of tissue copper stores. Rats in this group were switched to a triethylenetetramine-free copper-deficient diet 1 week prior to mating. Dams in the diabetic and control groups were fed a control (8 micrograms copper, 25 micrograms zinc/g) diet throughout the study. On GD 3.0, one subset of the control dams was assigned to the zinc-deficient group (ZnD) and fed a zinc-deficient diet. A second subset of control dams was assigned to a restricted fed group and fed the control diet in quantities consumed by the zinc-deficient dams. Litters were taken by cesarean section on GD 11.0. Embryos were examined for gross morphology and assessed for patterns of cell death using Nile blue sulfate. Embryos from the CuD dams were characterized by edematous hindbrain. Embryos from the diabetic group were characterized by delayed development. Altered patterns of cell death were only detected in embryos from the ZnD dams. Within the ZnD group, embryos were either characterized by small size, edematous head region, and control patterns of cell death, or normal size, normal morphology, and increased cell death. These different patterns of morphology and cell death in the embryos of ZnD dams were associated with different patterns of maternal food intake.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of maternal diabetes and dietary copper on fetal development in rats.

To test whether diabetes associated alterations in copper metabolism contribute to diabetes-induced teratogenicity in rats, pregnancy outcome was compared between diabetic and nondiabetic rats fed either a copper adequate (12 micrograms/g diet) or low copper diet (1 microgram/g diet). The dietary regimen was begun two weeks prior to mating and continued throughout pregnancy. To facilitate the reduction of maternal copper stores in the low copper groups, the low copper diet was supplemented with a copper chelator, triethylenetetraamine, at 1% for one week; the chelator was removed from the diet one week prior to mating. Pregnancy was terminated on gestation day 20. Maternal and fetal tissues were assessed for copper concentrations, the activities of the cuproenzymes copper, zinc superoxide dismutase and ceruloplasmin, and the copper binding protein metallothionein. Dams fed the low copper diet had low tissue copper concentrations, and low plasma ceruloplasmin and erythrocyte superoxide dismutase activities compared to copper-adequate dams. Fetuses in the low copper groups were characterized by low liver copper concentrations. Gross structural and skeletal anomalies were only observed in the diabetic groups; maternal copper intake did not influence the frequency of these anomalies. However, fetuses in the low-copper nondiabetic group, and both diabetic groups, were characterized by low liver copper, zinc superoxide dismutase activity suggesting that fetal copper metabolism was influenced by both copper intake and diabetes.