An inverted cAMP response element mediates the cAMP induction of the ovine beta 1-adrenergic receptor gene

We identified an inverted, functional cAMP response element (CRE) located at--1599 bp relative to the translation start site within the ovine beta 1-adrenergic receptor (beta 1 AR) gene promoter. In transfection studies with SK-N-MC cells, a 40-bp oligonucleotide containing the potential CRE, beta 1 AR-CRE, conferred a 3- to 4-fold increase in luciferase activity mediated by cAMP. The induction was mimicked by co-transfecting the cells with a vector overexpressing the alpha-catalytic subunit of the cAMP-dependent protein kinase (PKA) without treatment, and was blocked by overexpressing a PKA inhibitor (PKI). In electrophoretic mobility shift assays, a discrete binding pattern was shown in cell nuclear extract probed with the 40 bp beta 1 AR-CRE. The binding was shown to be specific and supershifted by addition of a CRE binding protein (CREB-1) antibody. These data demonstrate that cAMP mediates the induction of beta 1 AR gene expression by interacting with an inverted CRE within the promoter region. This is the first reported functional CRE among all beta 1 AR genes.     

D1 receptors mediate dopamine action in the fetal suprachiasmatic nuclei: studies of mice with targeted deletion of the D1 dopamine receptor gene

Studies in rodents suggest the presence of a dopaminergic system that influences the function of a biological clock in the hypothalamic suprachiasmatic nuclei (SCN). To provide insights into mechanisms of dopamine action in the SCN, we studied transgenic mice that had either one allele (+?-) or both alleles (-/-) of the D1 dopamine receptor gene deleted, along with normal (+/+) littermates. As expected, receptor labelling autoradiography studies using [125I]SCH 23982 showed a complete absence of D1 dopamine receptor binding sites in the SCN of -/- animals. When pregnant mice from +?- x +?- matings were injected with the D1 receptor agonist SKF 38393, or the dopamine reuptake blocker GBR 12909 at day 19 of gestation, c-fos mRNA expression was observed in the SCN of +/+ fetuses. In contrast, c-fos mRNA induction was not seen in -/- or +?- litter mates. Injection of cocaine into pregnant dams also resulted in robust SCN c-fos mRNA expression in +/+ mice. Increases in SCN c-fos mRNA expression were also seen in +?- and -/- mice suggesting that cocaine action in the SCN involves both D1 receptor-dependent and -independent mechanisms. Collectively, our studies of transgenic mice deficient in D1 receptors support the presence of a functional dopaminergic system in the fetal SCN. We also identify D1 receptors as the prominent transducer of dopamine action in the fetal SCN.     

Restoration of norepinephrine and reversal of phenotypes in mice lacking dopamine beta-hydroxylase

Mice with a targeted disruption of the dopamine beta-hydroxylase (DBH) gene are unable to synthesize norepinephrine (NE) and epinephrine. These mice have elevated levels of dopamine in most tissues, although the levels are only a fraction of those normally found for NE. It is noteworthy that NE can be restored to normal levels in many tissues after a single injection of the synthetic amino acid precursor of NE, L-threo-3,4-dihydroxyphenylserine (DOPS). In other tissues, NE can be restored to normal levels after multiple injections of DOPS, whereas in the midbrain and cerebellum, restoration of NE is limited to 25-30% of normal. NE levels typically peak approximately 5 h after DOPS administration and are undetectable by 48 h. Epinephrine levels are more difficult to restore. The elevated levels of dopamine fall modestly after injection of DOPS. S(-)-Carbidopa, which does not cross the blood-brain barrier, inhibits aromatic L-amino acid decarboxylase and effectively prevents restoration of NE by DOPS in the periphery, while allowing restoration in the CNS. Ptosis and reductions in male fertility, hind-limb extension, postdecapitation convulsions, and uncoupling protein expression in dopamine beta-hydroxylase-deficient mice are all reversed by DOPS injection.     

Effect of two inhibitors of dopamine beta-hydroxylase on maturation of memory in mice

HL-A antigens of 35 patients with Beh?et's disease and 36 normal Japanese were determined by a standard microlymphocytotoxicity test. The frequency of HL-A5 among patients was significantly higher than the controls. No significant differences were observed in the distribution of other HL-A antigens.     

Effect of variations in adrenocortical function on dopamine beta-hydroxylase and norepinephrine in the brain of the rat

The effect of adrenalectomy and corticosterone treatment on dopamine beta-hydroxylase (DBH) activity, catecholamine content and norepinephrine formation and metabolism were studied in the hypothalamus and other parts of the brain of male rats. Two days after adrenalectomy, there was a decrease in DBH activity in the hypothalamus and the brain stem but no change in norepinephrine or dopamine content. Conversion of intraventricularly administered tritiated dopamine to tritiated norepinephrine was slightly increased and norepinephrine was metabolized at a more rapid rate than normal. Corticosterone in a dose of 100 mg/kg increased DBH activity but decreased hypothalamic norepinephrine and copamine content. In adrenalectomized rats, smaller, more physiological doses of corticosterone did not change DBH activity or catecholamine content. The fact that norepinephrine formation and metabolism were increased at the same time that DBH activity in vitro was decreased suggests that DBH is not rate-limiting in adrenergic neurons in the hypothalamus, or that a change in the in vitro activity of the enzyme was not accompanied by a parallel change in its activity in vivo.     

Adrenal origin of the increase in plasma dopamine beta-hydroxylase and catecholamines induced by hemorrhagic hypotension in dogs

Controlled hemorrhagic hypotension in anesthetized dogs causes progressive increases in dopamine beta-hydroxylase (DBH) and catecholamine (CA) plasma levels and in heart rate. The concentration (units per milliliter) and the calculated total plasma content of DBH activity [(units circulating + reservoir + samples] increased 2.6 and 2.3 times, respectively. A significant positive correlation (P less than .001) was found between the plasma levels of DBH and CA; however, the CA plasma levels increased earlier and were of greater magnitude (10-fold) than those of DBH. These results suggest that CAs are more sensitive indicators of acute changes in adrenergic activity than DBH. Surgical bilateral adrenalectomy completely abolished the increases in circulating CA and DBH levels and in heart rate induced by the hemorrhage, independently of the percentage of blood removed. These results indicate that the adrenal glands contribute almost exclusively to the rise in plasma DBH and CA caused by the bleeding stress and that high circulating CA concentrations seem to account for the tachycardia that accompanies the hemorrhagic hypotension. The infusion of the reservoir blood with a lower DBH and CA content than that present in the animal at that time produced a rapid fall in circulating CA levels (59.2 +/- 8.9 to 10.8 +/- 3.3 ng/ml) and no change in the DBH concentration (5.43 +/- 0.42 and 5.40 +/- 0.53 U/ml). A 38% increase in the calculated total plasma content of DBH occurred with the transfusion. Due to the large size of the DBH molecules, trapping in tissues during the hemorrhagic hypotension period might have occurred. The improvement in the hemodynamic conditions caused by the transfusion would facilitate the washout of the enzyme from the tissues into the circulation.     

Cardiovascular effects of nepicastat (RS-25560-197), a novel dopamine beta-hydroxylase inhibitor

PURPOSE: The aim of the present study was to develop a standard protocol for evaluating peak oxygen uptake and anaerobic threshold during upper body work by cross-country skiers. METHODS: All tests were performed on a specially developed ski ergometer and incorporated the double poling technique. In series I, continuous and discontinuous protocols for measuring VO2peak at different inclinations of the ski ergometer were performed. In series II, a protocol for evaluating anaerobic threshold during upper body work was established. Eleven well trained regional male cross-country skiers participated in the study. All tests in each series were carried out during a period of 14 d. RESULTS: VO2peak did not differ using continuous or discontinuous protocol while working on the ski ergometer. Inclination was found to influence VO2peak, which was reduced at 7 degrees compared with 3 degrees, 5 degrees, and 6 degrees. Th(an) working on the ski ergometer was reached at a power output, VO2, or fc, which gave on average a blood lactate concentration of 1.8 mmol.L-1 higher than those found after the warm-up period during a graded protocol. CONCLUSIONS: Testing only the traditional Th(an) and VO2max while running on a treadmill hides important determinants of endurance in cross-country skiing as shown by that no correlation was found between VO2max and VO2peak in the present study.     

Effects of calcium and phosphate on catecholamines, ATP and dopamine beta-hydroxylase of chromaffin medullary granules

The penetration into the single layers of human skin in vitro of 17 alpha-estradiol, 17 beta-estradiol and estriol was investigated. The radiolabeled substances were incorporated into 4 standard ointments and into an alcoholic solution mixture. After application to the skin and after different penetration periods, the horny layer was taken off by adhesive tape stripping. The epidermis and the dermis were separated by slicing them down parallel to the skin surface in a freeze microtome. In each single layer, the amount of substance was determined and calculated relative to the applied quantity and in absolute concentrations (mug per tissue weight and molarity). Besides the expected dependence of the penetration on the type of ointment, there is a distinct dependence on the chemical structure: estriol penetrates considerably slower and in less concentrations into the living layers of the human skin than the estradiols. Furthermore, estriol reaches the dermis only in low concentrations so that this substance may be termed epidermotropic. 17 alpha-estriol which has only weak sexhormone properties in humans penetrates as well as the sexhormone 17 beta-estradiol.     

Redox gene therapy for ischemia/reperfusion injury of the liver reduces AP1 and NF-kappaB activation

Magnaporthe grisea, the causal agent of rice blast, forms a dome-shaped melanized infection structure, an appressorium, to infect its host. Environmental cues that induce appressorium formation by this fungus include hydrophobicity and hardness of contact surface, and chemicals from the host. To determine if the calcium/calmodulin-dependent signaling systems are involved in appressorium formation in M. grisea, we tested the effects of the calcium chelator, calcium ionophore, diverse intracellular calcium modulators, and calmodulin antagonists on appressorium formation. Several calcium modulators and calmodulin antagonists inhibited appressorium formation at the microM level, while conidia germination remained unaffected. There was an inhibition of appressorium formation by EGTA, a calcium chelator, which was restored by the addition of exogenous CaCl2. Neomycin, a phospholipase C inhibitor, specifically inhibited appressorium formation at concentrations from 10 microM to 100 mM. These data suggest that a calcium/calmodulin-dependent signaling system is involved in the appressorium formation of M. grisea.     

Two transmembrane signaling mechanisms control expression of the cAMP receptor gene CAR1 during Dictyostelium development

Dictyostelium discoideum is among the best characterized organisms for the study of receptor/guanine nucleotide binding protein-mediated control of differentiation. Dictyostelium grow unicellularly but form fully differentiated multicellular organisms through a developmental program regulated by secreted cAMP activating specific cell-surface receptors. Dictyostelium respond differentially to cAMP at different developmental stages. During early development, expression of certain genes is induced by low-level oscillations of extracellular cAMP. Later, continuous, high cAMP concentrations will promote expression of specific genes in multicellular structures. Here, we show that the cAMP receptor gene CAR1, which is essential for development, utilizes two promoters that are activated at distinct stages of development and respond to different extracellular cAMP conditions. One promoter is active with low-level oscillations of cAMP; exposure to high cAMP concentrations will repress this promoter and induce a second promoter. The CAR1 mRNAs are alternatively spliced but encode identical proteins. Thus, through differential sensitivity to its own ligand, cAMP, two promoters and alternative splicing regulate CAR1 expression during Dictyostelium development.     

ADP-ribosylation factor proteins mediate agonist-induced activation of phospholipase D

The role of small G proteins of the ADP-ribosylation factor (ARF) and Rho families on the activation of phospholipase D (PLD) by platelet-derived growth factor (PDGF) and phorbol esters (PMA) has been investigated. The activation of PLD by PDGF and PMA was blocked by brefeldin A (BFA), an inhibitor of ARF activation, but not by Clostridium botulinum C3 exotoxin, an inhibitor of the activity of Rho. PDGF and PMA, in the presence of GTPgammaS, promoted the association of ARF and RhoA with cell membranes. Cells depleted of ARF and Rho by digitonin permeabilization showed a significant reduction of the activity of phospholipase D. Recombinant ARF was sufficient to restore agonist-induced PLD activity to digitonin-permeabilized, cytoplasm-depleted cells. In contrast, isoprenylated recombinant RhoA had no effects in this reconstitution assay. HIRcB cells were transiently transfected with wild-type and dominant-negative mutants of ARF1 and ARF6. Neither wt-ARF1 nor wt-ARF6 had any effects on agonist-dependent PLD activity. However, dominant-negative ARF1 and ARF6 mutants blocked the stimulation of PLD by PDGF but only partially inhibited the effects of PMA. These results demonstrate that ARF rather than Rho proteins mediate the activation of PLD by PDGF and phorbol esters in HIRcB fibroblasts.