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1.
Mann Stephanie E.; Nijland Mark J.M.; Ross Michael G. 《Journal of applied physiology》1996,81(6):2588-2594
Mann, Stephanie E., Mark J. M. Nijland, and Michael G. Ross.Ovine fetal adaptations to chronically reduced urine flow: preservation of amniotic fluid volume. J. Appl.Physiol. 81(6): 2588-2594, 1996.Adequateamniotic fluid (AF) volume is maintained by a balance of fetal fluidproduction (lung liquid and urine) and resorption (swallowing andintramembranous flow). Because fetal urine is the principle source ofAF, alterations in urine flow and composition directly impact AFdynamics. Intra-amniotic 1-desamino-8-D-argininevasopressin (DDAVP) is rapidly absorbed into fetal plasma and induces amarked fetal urinary antidiuresis. To examine the effect ofintra-amniotic- DDAVP-induced fetal urinary responses on AF volume andcomposition, six chronically prepared ewes with singleton fetuses(gestation 128 ± 2 days) were studied for 72 h after a singleintra-amniotic DDAVP (50-µg) injection. After DDAVP, fetal urineosmolality significantly increased at 2 h (157 ± 13 to 253 ± 21 mosmol/kg) and remained elevated at 72 h (400 ± 13 mosmol/kg). Urinary sodium (33.0 ± 4.5 to 117.2 ± 9.7 meq/l)and chloride (26.0 ± 2.8 to 92.4 ± 8.1 meq/l) concentrations similarly increased. AF osmolality increased (285 ± 3 to 299 ± 4 mosmol/kgH2O), although there was no change in fetalplasma osmolality (294 ± 2 mosmol/kg). Despite a 50% reductionin fetal urine flow (0.12 ± 0.03 to 0.05 ± 0.02 ml · kg1 · min1at 2 h and 0.06 ± 0.01 ml · kg1 · min1after 72 h), AF volume did not change (693 ± 226 to 679 ± 214 ml). There were no changes in fetal arterial blood pressures, pH,PCO2, orPO2 after DDAVP. We conclude the following. 1)Intra-amniotic DDAVP injection induces a prolonged decrease in fetalurine flow and increases in urine and AF osmolalities. 2) Despite decreased urine flow, AFvolume does not change. We speculate that, in response to DDAVP-inducedfetal oliguria, reversed intramembranous flow (from isotonic fetalplasma to hypertonic AF) preserves AF volume. 相似文献
2.
Hazrat Ali Marco I. Ries Jeroen G. Nijland Peter P. Lankhorst Thomas Hankemeier Roel A. L. Bovenberg Rob J. Vreeken Arnold J. M. Driessen 《PloS one》2013,8(6)
Profiling and structural elucidation of secondary metabolites produced by the filamentous fungus Penicillium chrysogenum and derived deletion strains were used to identify the various metabolites and enzymatic steps belonging to the roquefortine/meleagrin pathway. Major abundant metabolites of this pathway were identified as histidyltryptophanyldiketopiperazine (HTD), dehydrohistidyltryptophanyldi-ketopiperazine (DHTD), roquefortine D, roquefortine C, glandicoline A, glandicoline B and meleagrin. Specific genes could be assigned to each enzymatic reaction step. The nonribosomal peptide synthetase RoqA accepts L-histidine and L-tryptophan as substrates leading to the production of the diketopiperazine HTD. DHTD, previously suggested to be a degradation product of roquefortine C, was found to be derived from HTD involving the cytochrome P450 oxidoreductase RoqR. The dimethylallyltryptophan synthetase RoqD prenylates both HTD and DHTD yielding directly the products roquefortine D and roquefortine C without the synthesis of a previously suggested intermediate and the involvement of RoqM. This leads to a branch in the otherwise linear pathway. Roquefortine C is subsequently converted into glandicoline B with glandicoline A as intermediates, involving two monooxygenases (RoqM and RoqO) which were mixed up in an earlier attempt to elucidate the biosynthetic pathway. Eventually, meleagrin is produced from glandicoline B involving a methyltransferase (RoqN). It is concluded that roquefortine C and meleagrin are derived from a branched biosynthetic pathway. 相似文献
3.
Jongbloed JD Grieger U Antelmann H Hecker M Nijland R Bron S van Dijl JM 《Molecular microbiology》2004,54(5):1319-1325
Activity of the Tat machinery for protein transport across the inner membrane of Escherichia coli and the chloroplast thylakoidal membrane requires the presence of three membrane proteins: TatA, TatB and TatC. Here, we show that the Tat machinery of the Gram-positive bacterium Bacillus subtilis is very different because it contains at least two minimal Tat translocases, each composed of one specific TatA and one specific TatC component. A third, TatB-like component is apparently not required. This implies that TatA proteins of B. subtilis perform the functions of both TatA and TatB of E. coli and thylakoids. Notably, the two B. subtilis translocases named TatAdCd and TatAyCy both function as individual, substrate-specific translocases for the twin-arginine preproteins PhoD and YwbN, respectively. Importantly, these minimal TatAC translocases of B. subtilis are representative for the Tat machinery of the vast majority of Gram-positive bacteria, Streptomycetes being the only known exception with TatABC translocases. 相似文献
4.
Bishai JM Penninga L Nijland R Meulenaar R Gheorghe CP Zhao Y Buchholz JN Zhang L Longo LD 《American journal of physiology. Regulatory, integrative and comparative physiology》2002,282(6):R1654-R1662
In ovine cerebral arteries, adrenergic-mediated vasoconstrictor responses differ significantly with developmental age. We tested the hypothesis that, in part, these differences are a consequence of altered alpha(2)-adrenergic receptor (alpha(2)-AR) density and/or affinity. In fetal (approximately 140 days) and adult sheep, we measured alpha(2)-AR density and affinity with the antagonist [(3)H]idazoxan in main branch cerebral arteries and other vessels. We also quantified contractile responses in middle cerebral artery (MCA) to norepinephrine (NE) or phenylephrine in the presence of the alpha(2)-AR antagonists yohimbine and idazoxan and contractile responses to the alpha(2)-AR agonists clonidine and UK-14304. In fetal and adult cerebral artery homogenates, alpha(2)-AR density was 201 +/- 18 and 52 +/- 6 fmol/mg protein, respectively (P < 0.01); however, antagonist affinity values did not differ. In fetal, but not adult, MCA, 10(-7) M yohimbine significantly decreased the pD(2) for NE-induced tension in the presence of 3 x 10(-5) M cocaine, 10(-5) M deoxycorticosterone, and 10(-6) M tetrodotoxin. In fetal, but not adult, MCA, UK-14304 induced a significant decrease in pD(2) for the phenylephrine dose-response relation. In addition, stimulation-evoked fractional NE release was significantly greater in fetal than in adult cerebral arteries. In the presence of 10(-6) M idazoxan to block alpha(2)-AR-mediated inhibition of prejunctional NE release, the fractional NE release was significantly increased in both age groups. We conclude that in fetal and adult ovine cerebral arteries, alpha(2)-AR appear to be chiefly prejunctional. Nonetheless, the fetal cerebral arteries appear to have a significant component of postjunctional alpha(2)-AR. 相似文献
5.
Molnar J Nijland MJ Howe DC Nathanielsz PW 《American journal of physiology. Regulatory, integrative and comparative physiology》2002,283(3):R561-R567
Dexamethasone (DM) was administered to pregnant ewes as three weekly courses of four injections of 2 mg at 12-h intervals. DM (n = 7) or saline (n = 7) was given starting at 103 days of gestation (dGA; term approximately 149 days). Fetal femoral arteries (approximately 300-microm internal diameter) were evaluated using wire myography at 119 dGA. DM-exposed fetuses were significantly smaller than saline-exposed fetuses. DM exposure increased maximal contraction to 125 mM KCl, and maximum tension developed along with sensitivity to endothelin-1 and relaxation to bradykinin. Preincubation with the nitric oxide synthase inhibitor N(G)-nitro-L-arginine methyl ester shifted the dose-response curves to endothelin-1 and acetylcholine to the right in controls but not in the DM-exposed group. Relaxation to acetylcholine and to the nitric oxide donor sodium nitroprusside was similar in both groups. The combination of enhanced endothelin-induced vasoconstriction, abnormal endothelium-dependent relaxation, and normal endothelium-independent relaxation indicates microvessel dysfunction following antenatal DM administration. Because such dysfunction is associated with several forms of adult hypertension, our results indicate the potential for consequences of antenatal glucocorticoid exposure on adult cardiovascular health. 相似文献
6.
Roberts TJ Caston-Balderrama A Nijland MJ Ross MG 《American journal of physiology. Endocrinology and metabolism》2000,279(3):E494-E500
We hypothesized that central neuropeptide Y (NPY) increases swallowing activity and alters renal function in the near-term ovine fetus. Six ewes with singleton fetuses (130 +/- 2 days of gestation; 148 days = term) were chronically prepared with arterial and venous catheters, a fetal lateral cerebroventricular cannula, and fetal bladder and amniotic fluid catheters. For determination of fetal swallowing, electromyogram wires were placed in the fetal thyrohyoid muscle and the upper and lower nuchal esophagus. Electrodes were implanted on the parietal dura for determination of fetal electrocorticogram (ECoG). After 5 days of recovery, fetal swallowing, ECoG, blood pressure, and heart rate were monitored during a 3-h basal period. At t = 3 h, ovine NPY (0.05 mg/kg) was administered into the lateral ventricle, and fetuses were monitored for an additional 8 h. A control study of central administration of artificial cerebral spinal fluid was performed on an alternate day. Central NPY significantly increased swallowing activity during low-voltage ECoG from basal activity (1.26 +/- 0.15 swallows/min) at 4 h (1.93 +/- 0.37 swallows/min), 6 h (1.69 +/- 0.27 swallows/min), and 8 h (2.38 +/- 0.31 swallows/min). NPY significantly increased fetal urine flow (basal: 0.13 +/- 0.02; 4 h: 0.21 +/- 0.04; 6 h: 0. 19 +/- 0.03 ml.kg(-1).min(-1)). These results demonstrate that central NPY stimulates fetal swallowing activity and increases urine output, which may contribute to the in utero development of ingestive behavior. 相似文献
7.
Josep C Jiménez-Chillarón Mark J Nijland António A Ascens?o Vilma A Sard?o José Magalh?es Michael J Hitchler Frederick E Domann Paulo J Oliveira 《Epigenetics》2015,10(4):259-273
Epigenetics, or regulation of gene expression independent of DNA sequence, is the missing link between genotype and phenotype. Epigenetic memory, mediated by histone and DNA modifications, is controlled by a set of specialized enzymes, metabolite availability, and signaling pathways. A mostly unstudied subject is how sub-toxic exposure to several xenobiotics during specific developmental stages can alter the epigenome and contribute to the development of disease phenotypes later in life. Furthermore, it has been shown that exposure to low-dose xenobiotics can also result in further epigenetic remodeling in the germ line and contribute to increase disease risk in the next generation (multigenerational and transgenerational effects). We here offer a perspective on current but still incomplete knowledge of xenobiotic-induced epigenetic alterations, and their possible transgenerational transmission. We also propose several molecular mechanisms by which the epigenetic landscape may be altered by environmental xenobiotics and hypothesize how diet and physical activity may counteract epigenetic alterations. 相似文献
8.
Maternal nutrient restriction reduces concentrations of amino acids and polyamines in ovine maternal and fetal plasma and fetal fluids 总被引:7,自引:0,他引:7
Kwon H Ford SP Bazer FW Spencer TE Nathanielsz PW Nijland MJ Hess BW Wu G 《Biology of reproduction》2004,71(3):901-908
Amino acids and polyamines are essential for placental and fetal growth, but little is known about their availability in the conceptus in response to maternal undernutrition. We hypothesized that maternal nutrient restriction reduces concentrations of amino acids and polyamines in the ovine conceptus. This hypothesis was tested in nutrient-restricted ewes between Days 28 and 78 (experiment 1) and between Days 28 and 135 (experiment 2) of gestation. In both experiments, ewes were assigned randomly on Day 28 of gestation to a control group fed 100% of National Research Council (NRC) nutrient requirements and to an nutrient-restricted group fed 50% of NRC requirements. Every 7 days beginning on Day 28 of gestation, ewes were weighed and rations adjusted for changes in body weight. On Day 78 of gestation, blood samples were obtained from the uterine artery and umbilical vein for analysis. In experiment 2, nutrient-restricted ewes on Day 78 of gestation either continued to be fed 50% of NRC requirements or were realimented to 100% of NRC requirements until Day 135. Fetal weight was reduced in nutrient-restricted ewes at both Day 78 (32%) and Day 135 (15%) compared with controls. Nutritional restriction markedly reduced (P < 0.05) concentrations of total alpha-amino acids (particularly serine, arginine-family amino acids, and branched-chain amino acids) and polyamines in maternal and fetal plasma and in fetal allantoic and amniotic fluids at both mid and late gestation. Realimentation of nutrient-restricted ewes increased (P < 0.05) concentrations of total alpha-amino acids and polyamines in all the measured compartments and prevented intrauterine growth retardation. These novel findings demonstrate that 50% global nutrient restriction decreases concentrations of amino acids and polyamines in the ovine conceptus that could adversely impact key fetal functions. The results have important implications for understanding the mechanisms responsible for both intrauterine growth retardation and developmental origins of adult disease. 相似文献
9.
By rewiring the sporulation gene-regulatory network of Bacillus subtilis, we generated a novel expression system relying on derepression. The gene of interest is placed under the control of the abrB promoter, which is active only when Spo0A is absent, and Spo0A is controlled via an IPTG (isopropyl-beta-d-thiogalactopyranoside)-inducible promoter. 相似文献
10.