Increasing energy efficiency and sensitivity with simple sensor platforms.

We outline and review an approach to the construction of conductometric sensors that demonstrate considerably higher sensitivities than traditional metal oxide sensors. Simple sensor platforms do not require film-based technology, operate at room temperature, and can be obtained without the use of time consuming self-assembly processes. A combined nanopore coated micro-porous array is deposited with nanostructure directing acidic metal oxide island sites which vary in their Lewis acidity, decorate the micropores, and control an electron transduction process. The interaction of analytes with these island sites varies in a predictable manner and can be modified through in-situ functionalization of their Lewis acidity. The micropores allow rapid Fickian diffusion of analytes to the active nanostructured island sites whose reversible interaction with the analyte dominates the sensor response. We require only that the island sites be deposited at sufficiently low concentration so as not to interact electronically with each other. Highly accurate repeat placement of the depositions is not required. The nanoporous walls of the microarray act as a phase match for the deposition of a diversity of nanostructures that are selected for deposition from a variety of easily obtained solution-based sources as the forgiving deposition process requires a minimum of energy consumption and time. Comparisons to a variety of metal oxide systems are considered. Observed sensitivities and the sensor system reversibility can be predicted from the recently developing IHSAB model.

Characterization and pharmacological studies of an octopamine-sensitive adenylate cyclase from nerve cord of Locusta migratoria.

An octopamine-sensitive adenylate cyclase that is insensitive to stimulation by dopamine (DA) and 5-hydroxytryptamine (5-HT), was studied in a homogenized nerve cord preparation of the migratory locust, Locusta migratoria. The enzyme complex is similar to catecholamine-sensitive cyclases from mammals with respect to pH-optimum, requirement for Mg++ and GTP, and sensitivity to forskolin. The octopamine-mediated elevation of adenylate cyclase activity is antagonized by a variety of drugs with the following order of potency: mianserin greater than phentolamine greater than promethazine greater than gramine greater than cyproheptadine greater than cis-flupenthixol greater than chlorpromazine greater than metoclopramide.

Stimulation of carbohydrate metabolising enzymes by synthetic hypertrehalosemic peptides in thoracic musculature of the American cockroach, Periplaneta americana.

The ability of the synthetic hypertrehalosemic peptides, HT-I and HT-II, to influence the activities of glycogen phosphorylase, trehalase and hexokinase via elevation of Ca++ and cAMP levels was examined in thoracic musculature of the American cockroach, Periplaneta americana. The peptides effect dose- and time-dependent activation of phosphorylase, trehalase and hexokinase activities that occur concomitantly with elevated levels of intracellular calcium. In addition, HT-I increases the accumulation of cyclic AMP in muscle cells.

Modulation of octopamine-mediated production of cyclic AMP by phorbol-ester-sensitive protein kinase C in an insect cell line.

The presence of protein kinase C (EC 2.7.1.37) in an insect cell line has been demonstrated. Phorbol 12-myristate 13-acetate (PMA), in micromolar concentrations, activated protein kinase C with a translocation of the enzyme from the cytosol to the particulate fraction. Cyclic AMP production in the presence of PMA, octopamine and a combination of both increased in a dose-dependent and time-dependent fashion. The biologically inactive 4 alpha-phorbol 12,13-didecanoate had no effect on protein kinase C activity or on octopamine-mediated cyclic AMP production. Pretreatment of the cells with pertussis toxin had no effect on the response of cells to octopamine or PMA. However, pretreatment with cholera toxin resulted in increased cyclic AMP production which was further enhanced when both cholera toxin and PMA were used in combination. Our data indicate that the octopamine-mediated cyclic AMP production is modulated by protein kinase C.

Pharmacological characterisation of the dopamine-sensitive adenylate cyclase in cockroach brain: evidence for a distinct dopamine receptor.

Dopamine increases cyclic AMP production in crude membrane preparations of cockroach brain with plateaus in cyclic AMP production occurring between 1-10 microM and at 10 mM. Maximal production of cyclic AMP is 2.25 fold greater than that of control values. Octopamine also increases cyclic AMP production with a Ka of 1.4 microM and maximal production 3.5 fold greater than that of control. 5-Hydroxytryptamine does not increase cyclic AMP production. The effects of octopamine and dopamine are fully additive. The vertebrate dopamine agonists ADTN and epinine stimulate the dopamine-sensitive adenylate cyclase (AC) with Ka values of 4.5 and 0.6 microM respectively and with maximal effectiveness 1.7 fold greater than that of control. The selective D2-dopamine agonist LY-171555 stimulates cyclic AMP production to a similar extent with a Ka of 50 microM. Other dopamine agonists (apomorphine, SKF-82526, SKF-38393) have no stimulatory effects. The octopamine-sensitive AC is inhibited by a variety of antagonists known to affect octopamine and dopamine receptors, with the following order of potency: mianserin greater than phentolamine greater than cyproheptadine greater than piflutixol greater than cis-flupentixol greater than SCH-23390 greater than (+)-butaclamol greater than SKF-83566 greater than SCH-23388 greater than sulpiride greater than spiperone greater than haloperidol. The dopamine-sensitive AC is inhibited by the same compounds with the following order of potency: piflutixol greater than cis-flupentixol greater than (+)-butaclamol greater than spiperone greater than or equal to SCH-23390 greater than cyproheptadine greater than SKF-83566 greater than SCH 23388 greater than mianserin greater than phentolamine greater than sulpiride greater than haloperidol. With the exception of mianserin, 3H-piflutixol is displaced from brain membranes by dopamine antagonists with an order of potency similar to that observed for the inhibition of dopamine-sensitive AC. The results indicate that the octopamine- and dopamine-sensitive AC in cockroach brain can be distinguished pharmacologically and the dopamine receptors coupled to AC have pharmacological characteristics distinct from vertebrate D1- and D2-dopamine receptors.

Forskolin-insensitive adenylate cyclase in cultured cells of Choristoneura fumiferana (Insecta).

Adenylate cyclase from a spruce budworm cell line, IBRI-Cfl, is activated by octopamine (Ka = 50 microM), guanine nucleotides and sodium fluoride but not by forskolin. In addition, forskolin does not potentiate the octopamine-sensitive response. To our knowledge, this is the first published report of a hormone-sensitive adenylate cyclase, with a functional guanine nucleotide regulatory protein, that is insensitive to forskolin both in intact cells and washed membrane preparations.

Pharmacology of aminergic receptors mediating an elevation in cyclic AMP and release of hormone from locust neurosecretory cells.

Synaptic activation of the neurosecretory cells within the glandular lobe of the corpus cardiacum of locusts results in the release of bioassayable adipokinetic hormones and an elevation in cAMP. The effectiveness of several putative aminergic neurotransmitters in mimicking these actions of the natural transmitter, and the effects of aminergic antagonists, have been studied. The receptors mediating the release of adipokinetic hormones exhibited a specificity for the monophenolic amines octopamine and synephrine at 10(-7) M. These two amines were also the most effective, at 5 X 10(-6) M, in elevating cAMP levels. Octopamine induced a dose-dependent elevation in cAMP with half-maximal stimulation occurring at 5 X 10(-6) M. 5-Hydroxytryptamine (5-HT) was also capable of elevating cAMP levels, but, unlike the octopamine response, or the response to the natural transmitter, the response to 5-HT was not blocked by the antagonist phentolamine. Gramine was also an effective antagonist of the octopamine-induced response. The results are consistent with the hypothesis that octopamine is the natural transmitter within this neurosecretory system.

Interaction of formamidines with octopamine-sensitive adenylate cyclase receptor in the nerve cord of Periplaneta americana L.

Chlordimeform (CDM) and demethylchloridimeform (DCDM) mimic the action of octopamine in elevating adenylate cyclase activity in intact nerve cords of the American cockroach, Periplaneta americana. At a concentration of 1 x 10(-5)M, DCDM (13.5x increase within 20 minutes) is a more potent effector of the response than CDM (3x increase within 20 minutes), but both compounds show less efficacy than octopamine (23.5x increase within 15 minutes). DCDM also mimics the stimulatory effect of octopamine on adenylate cyclase activity in nerve cord homogenates whereas CDM has no demonstrable effect on this preparation. The octopamine- and DCDM-induced responses are competitively inhibited by phentolamine (1 x 10(-6)M) and cyproheptadine (1 x 10(-6)M) but not by propranolol (1 x 10(-6)M). DCDM and CDM inhibit the octopamine-induced activation of adenylate cyclase by 33% and 44% respectively. The results are discussed in light of the proposal that DCDM serves as a partial agonist and CDM as an antagonist of the octopamine receptor.

Synaptic transmission elevates adenosine 3', 5'-monophosphate (cyclic AMP) in locust neurosecretory cells.

The release of adipokinetic hormones from the neurosecretory cells within the glandular lobe of the corpus cardiacum (CC) of locusts is under the synaptic control of axons within the nervi corporis cardiaca II (NCC II). This synapse has been shown to be aminergic with the transmitter tentatively identified as octopamine. We show here that stimulation of the presynaptic nerves in NCC II produces an increase in adenosine 3',5'-monophosphate (cyclic AMP) in the glandular lobe. Application of octopamine mimics the effect of nerve stimulation. These and other experiments lead us to believe the increase in cyclic AMP is coupled to the process of synaptic transmission, and that the increase occurs within the intrinsic neurosecretory cells of the glandular lobe.

Theoretical prediction of the vibrational spectra of group IB trimers.

The molecular structures of the group IB trimers, Cu(3), Ag(3), and Au(3), have been determined by using the semi-empirical diatomics-in-molecules theory. The trimers are found to have C(2v) symmetry with bond angles between 65 degrees and 80 degrees . The trimers are bound with respect to dissociation to the asymptotic limit of an atom plus a diatom. The binding energies per atom for Cu(3), Ag(3), and Au(3) are 1.08, 0.75, and 1.16 eV, respectively. The vibrational frequencies of the trimers have been determined for comparison with experimental results. The vibrational frequencies are characterized by low values for the bending and asymmetric stretch modes. The frequency of the symmetric stretch of the trimer is higher than the stretching frequency of the corresponding diatomic. A detailed comparison of the theoretical results with the previously measured Raman spectra of matrix isolated Ag(3) is presented.

Three-stage birefringent filter tuning smoothly over the visible region: theoretical treatment and experimental design.

The Jones transformation matrix, which describes the arbitrary incidence of polarized light on a thin uniaxial birefringent plate, is determined. With the optic axis presumed to lie in the plane of the plate, digital solutions to the resulting formulas are presented for several different quartz plates to depict the tuning characteristics of a birefringent plate functioning as a single-stage birefringent filter. A simplified model is used to generalize these results to describe a multistage birefringent filter. This theoretical study forms the basis for the design and construction of a three stage, quartz, birefringent filter to be used as the coarse tuning element in a visible cw dye laser. A relatively simple and straightforward procedure for the assembly of the three-stage filter is given. The performance of this newly constructed filter is found to be superior to currently available commercial models, tuning smoothly over the 4400-6600-A wavelength region.

CL regression in the pseudopregnant rabbit and the effects of treatment with prostaglandin F-2alpha and arachidonic acid.

During pseudopregnancy in the rabbit, plasma progesterone levels in the posterior vena cava fell rapidly from maximal concentrations of 9.8 +/- 0.7 (s.e.m.) ng/ml on Day 13 of pseudopregnancy to 2.0 +/- 0.6 ng/ml on Day 15. There was no significant increase in PGF levels at this time, although administration of indomethacin to a similar group of does delayed functional regression for over 7 days. Subcutaneous injection of 1 mg PGF-2alpha or 35 mg arachidonic acid on Day 9 of pseudopregnancy resulted in loss of luteal function as plasma progesterone levels fell significantly from about 6 to less than 1 ng/ml within 24 h. These findings indicate that the uterine factor responsible for luteolysis in the pseudopregnant rabbit may not be released in the form of PGF-2alpha.