Low loss Si(3)N(4)-SiO(2) optical waveguides on Si

We have developed an optical integrated circuit waveguide technology based on conventional Si processing. We demonstrate waveguide losses of <0.3 dB/cm in the 1.3-1.6-microm wavelength range. We use a high refractive-index core of Si(3)N(4) surrounded by SiO(2) cladding layers, which provides a highly confined optical mode adequate for butt coupling to channel substrate buried heterostructure lasers. We report the first IR transmission experiments in these waveguides and find two absorption peaks associated with H in SiO(2) and Si(3)N(4) layers at 1.40 and 1.52 microm, respectively. The peak absorptions are 2.2 and 1.2 dB/cm, respectively, and these peaks can be largely removed by annealing at 1100-1200 degrees C.

Low loss Bragg reflectors on SiO(2)-Si(3)N(4)-SiO(2) rib waveguides

The added waveguide attenuation loss associated with Bragg reflector formation is measured. The added scattering loss due to the roughness of the Bragg grating is found to be only 0.2 +/- 0.1 dB/cm for a Bragg reflector with a 15-A stop band. In addition to this background loss, attenuation resonances on the high energy side of the Bragg resonance are found. These are due to the contradirectional coupling of the fundamental waveguide mode into continuum modes of the Si(3)N(4) core layer and into the modes associated with the thick SiO(2) cladding layer. The coupling wavelengths of these resonances are in good agreement with theory.

Pedunculopontine tegmental nucleus of the rat: cytoarchitecture, cytochemistry, and some extrapyramidal connections of the mesopontine tegmentum

The pedunculopontine tegmental nucleus (PPTn) was originally defined on cytoarchitectonic grounds in humans. We have employed cytoarchitectonic, cytochemical, and connectional criteria to define a homologous cell group in the rat. A detailed cytoarchitectonic delineation of the mesopontine tegmentum, including the PPTn, was performed employing tissue stained for Nissl substance. Choline acetyltransferase (ChAT) immunostained tissue was then analyzed in order to investigate the relationship of cholinergic perikarya, dendritic arborizations, and axonal trajectories within this cytoarchitectonic scheme. To confirm some of our cytoarchitectonic delineations, the relationships between neuronal elements staining for ChAT and tyrosine hydroxylase were investigated on tissue stained immunohistochemically for the simultaneous demonstration of these two enzymes. The PPTn consists of large, multipolar neurons, all of which stain immunohistochemically for ChAT. It is present within cross-sections that also include the A-6 through A-9 catecholamine cell groups and is traversed by catecholaminergic axons within the dorsal tegmental bundle and central tegmental tract. The dendrites of PPTn neurons respect several nuclear boundaries and are oriented perpendicularly to several well-defined fiber tracts. Cholinergic axons ascend from the mesopontine tegmentum through the dorsal tegmental bundle and a more lateral dorsal ascending pathway. A portion of the latter terminates within the lateral geniculate nucleus. It has been widely believed that the PPTn is reciprocally connected with several extrapyramidal structures, including the globus pallidus and substantia nigra pars reticulata. Therefore, the relationships of pallidotegmental and nigrotegmental pathways to the PPTn were investigated employing the anterograde autoradiographic methodology. The reciprocity of tegmental connections with the substantia nigra and entopeduncular nucleus was investigated employing combined WGA-HRP injections and ChAT immunohistochemistry. The pallido- and nigrotegmental terminal fields did not coincide with the PPTn, but, rather, were located just medial and dorsomedial to it (the midbrain extrapyramidal area). The midbrain extrapyramidal area, but not the PPTn, was reciprocally connected with the substantia nigra and entopeduncular nucleus. We discuss these results in light of other cytoarchitectonic, cytochemical, connectional, and physiologic studies of the functional anatomy of the mesopontine tegmentum.

Oxidative phosphorylation of creatine by respiring pig heart mitochondria in the absence of added adenine nucleotides

Isolated pig heart mitochondria were found to form phosphocreatine continuously at the rate of 12.5 +/- 1.8 nmol per min per mg of the mitochondrial protein in the respiration medium without externally added adenine nucleotides, and its formation rate showed a concentration dependency with respect to creatine and phosphate. The synthesis of phosphocreatine was completely inhibited by antimycin, FCCP (carbonyl cyanide-p-trifluoromethoxyphenylhydrazone), and atractyloside. However, oligomycin had no effect on the rate of phosphocreatine formation. These results are discussed in terms of a model that heart mitochondrial creatine kinase is functionally coupled to the oxidative phosphorylating system via the action of the adenine nucleotide translocase.

The effects of new local anti-inflammatory steroids on leucocyte migration and prostanoid liberation in rats

The local anti-inflammatory potency of steroid-21-oate esters derived from prednisolone was determined by cotton pellet granuloma bioassay. The doses which inhibited granuloma formation by 50% (ID50) were: prednisolone, 0.5 mg/pellet; methyl 20 alpha-dihydroprednisolonate, 5.8 mg/pellet; methyl 20 beta-dihydroprednisolonate, 1.2 mg/pellet; methyl 17,20 alpha-acetonidodihydroprednisolonate, 6.0 mg/pellet. When administered at these equipotent local anti-inflammatory doses, only prednisolone depressed plasma corticosterone and promoted thymus involution. Prednisolone reduced neutrophil migration into saline-soaked polyester sponges and depressed the levels of 6-keto PGF1 alpha, PGE2 and elastase in the sponge-induced inflammatory exudate. Methyl 20 alpha- and 20 beta-dihydroprednisolonate had no effect on cell migration, but depressed the levels of 6-keto PGF1 alpha and elastase. The liberation of 6-keto PGF1 alpha, PGE2 and elastase and neutrophil migration were inhibited by methyl 17,20 alpha- and beta-acetonidodihydroprednisolonate, but the effect of the beta-epimer on cell migration was transient. These data suggest that steroid acid esters which have local and topical anti-inflammatory properties exert their effect in a similar fashion to glucocorticoids with a ketol side-chain (e.g. prednisolone) with respect to liberation of prostaglandins and lysosomal enzymes. However, their effect on neutrophil migration was variable, depending on their structural features. Furthermore, the systemic effects of these new derivatives were drastically reduced indicating that they may be of potential benefit in prolonged treatment.

Topical anti-inflammatory activity of esters of steroid 21-oic acids

Prednisolone derivatives, methyl 20 alpha- and 20 beta-dihydroprednisolonate and methyl 17,20 alpha- and 17,20 beta-acetonidodihydroprednisolonate have been evaluated for their topical anti-inflammatory activity in the croton oil induced ear edema test. The order of anti-inflammatory potency was prednisolone greater than methyl 17,20 alpha-acetonidodihydroprednisolonate greater than methyl 17,20 beta-acetonidodihydroprednisolonate greater than methyl 20 beta-dihydroprednisolonate greater than methyl 20 alpha-dihydroprednisolonate. This order was paralleled by the compounds' octanol-aqueous partition coefficients. Furthermore, after two consecutive days topical administration of an equipotent anti-inflammatory dose, only prednisolone significantly decreased plasma corticosterone levels and relative thymus weight, while the new steroid derivatives had no effect on these parameters, indicating their lack of systemic side effects.

Binding of ester and amide epimers of 20 zeta-dihydroprednisolonic acid to cytosol receptors and their acute pharmacological activities in rats

The competitive binding of two new classes of anti-inflammatory steroids, the esters and amides derived from the epimers of 20 zeta-dihydroprednisolonic acid, to cytosol receptors from rat liver and thymus was studied. The relative inhibition of [3H]dexamethasone binding by the steroid derivatives was the same, irrespective of the receptor source, with the following order: dexamethasone greater than prednisolone greater than methyl 17,20 alpha-acetonidodihydroprednisolonate greater than methyl 17,20 beta-acetonidodihydroprednisolonate greater than N-propyl 20 alpha-dihydroprednisolonamide greater than methyl 20 alpha-dihydroprednisolonate greater than methyl 20 beta-dihydroprednisolonate greater than N-propyl 20 beta-dihydroprednisolonamide. The alpha-epimer of the steroids always showed a higher binding affinity than the corresponding beta-epimer. In an acute pharmacological study, prednisolone induced the suppression of plasma corticosterone and an increase in tyrosine aminotransferase activity and glycogen content of rat liver. The esters and amides had no effect on these parameters except in the case of the acetonide derivatives of the steroid acid esters which slightly increased liver glycogen content.

Biochemical differences among four inosinate dehydrogenase inhibitors, mycophenolic acid, ribavirin, tiazofurin, and selenazofurin, studied in mouse lymphoma cell culture

The mechanism of the cellular toxicity of four inosinate dehydrogenase (IMP-DH) inhibitors with different antitumor and antiviral pharmacological profiles was investigated in mouse lymphoma (S-49) cell culture. Drug effects on cell growth, nucleotide pools, and DNA and RNA synthesis were measured in the presence and absence of guanine salvage supplies. Both guanine and guanosine were capable of bypassing the IMP-DH block, while they also demonstrated some growth-inhibitory effects when added alone in high concentrations. All four drugs reduced cellular guanosine triphosphate levels and caused secondary changes of the uridine, cytidine, and adenosine triphosphate pools that were similar among the four drugs. However, several drug effects in addition to IMP-DH inhibition were observed except with mycophenolic acid which may represent a pure IMP-DH inhibitor. Both tiazofurin and selenazofurin interfered with the uptake and/or metabolism of uridine and thymidine tracers; however, this effect appeared not to contribute to their cellular toxicity in vitro. Moreover, selenazofurin and tiazofurin impaired the utilization of exogenous guanine salvage supplies for DNA and RNA synthesis, and guanine was particularly ineffective in reversing the toxic effects of tiazofurin on cell growth. This finding is important in view of the available guanine salvage supplies in vivo. Since tiazofurin, selenazofurin, and their known metabolites failed to inhibit hypoxanthine-guanine-phosphoribosyl transferase, guanosine monophosphate kinase, and guanosine diphosphate kinase in cell extracts or permeabilized cells, these drugs may interfere with salvage transport across cellular membranes. The toxic effects of mycophenolic acid and ribavirin were similarly reversed by salvage supplies of up to 200 microM guanine, which suggests that ribavirin primarily acts as an IMP-DH inhibitor under these conditions. This result could explain the rather low antitumor efficacy of both mycophenolic acid and ribavirin in vivo. However, increasing the guanine salvage supply in the medium above 200 microM further reversed the toxic effects of mycophenolic acid to maximum rescue, while it increased the toxicity of ribavirin (300 microM). This finding suggests the presence of a toxic mechanism of ribavirin at higher concentrations that is dependent upon the presence of guanine supplies sufficient to fully overcome the IMP-DH inhibition. This study documents that each antimetabolite displays a unique spectrum of activities with multiple toxic targets.

Synthesis of a new anti-inflammatory steroidal acid ester: methyl 11 beta-hydroxy-3,20-dioxo-1,4-pregnadien-21-oate

The synthesis and anti-inflammatory activity of a new steroidal acid ester, methyl 11 beta-hydroxy-3,20-1,4-pregnadien-21-oate (5), are described. This compound has been prepared via three different synthetic routes. The first involves oxidation of the benzoate 3 to the aldehyde 4 followed by a Mattox-type rearrangement of the side chain in conjunction with elimination of the benzoyloxy group. The second method, prolonged reaction of 1-dehydrocorticosterone (8) with methanolic cupric acetate, affords methyl ester 5 in low yield. The third approach consists of selective oxidation at C-20 of the methyl 11 beta, 20 alpha and 20 beta-dihydroxy-3-oxo-1,4-pregnadien-21-oates (7a and 7b) with sulfur trioxide-pyridine complex. The local anti-inflammatory activities of the new ester 5 and intermediates 3, 4, 7a and 7b were determined by the cotton-pellet granuloma assay in rats. The anti-inflammatory activity of the title compound is equal to that of the parent steroid, prednisolone. However, unlike the latter compound, the ester does not cause reduction of adrenal and thymus weights or a lowering of plasma corticosterone levels.

Anti-inflammatory activity of the epimers of N-propyl 20 xi-dihydroprednisolonamide

The epimers of a steroid carboxamide, N-propyl 20 alpha- and 20 beta -dihydroprednisolonamide, were evaluated for their local and systemic effects on granuloma formation, pituitary-adrenal function and liver glycogen content in rats. When the carboxamides were administered locally, the 20 beta-epimer exhibited greater activity than the 20 alpha-epimer in suppressing cotton pellet granuloma formation. Neither epimer had suppressive effects on thymus weight and plasma corticosterone levels at the dose level used. When the carboxamides were administered systemically, they were pharmacologically inactive. Furthermore, in acute pharmacological studies, the carboxamides neither increased tyrosine aminotransferase activity and glycogen deposition in the liver nor decreased plasma corticosterone levels and relative thymus weight.

Temporal consistency of individual differences in cardiac response to a video game

Three experiments are reported which examined the temporal stability of cardiac reactions to a video game of the 'space invaders' genre. Experiment 1 also addressed the matter of inter-task consistency; in addition to the video game, subjects were presented with an unsignalled reaction time task and led to believe that relatively quick reactions attracted financial reward, while slower ones brought either a burst of loud noise or withdrawal of money previously earned. Forty-two male subjects were tested on both tasks on two occasions, a week apart. Of the two tasks, the video game elicited the greater reactivity. In addition, individual variations in reactivity showed striking temporal stability for both tasks. However, inter-task consistency was much less marked; in fact, a significant inter-task correlation was obtained only on the first occasion of testing. It is probable that limited consistency here was in some measure due to the ineffectiveness of our reaction time task in eliciting substantial reactivity. Finally, reactivity was independent of baseline heart rate level. In experiment 2, three extreme high and three extreme low cardiac reactors were selected from an initial sample of 23 male subjects, on the basis of reactivity during an initial session with the video game, and subsequently studied during four further sessions. Once more, impressive stability of heart rate reactivity was apparent over sessions. In experiment 3, we examined the reliability of individual variations in cardiac reactivity in women and the issue of whether temporal stability is constrained by menstrual cycle effects. Twenty-four females were tested on the video game both preovulatory and postovulatory, with half being tested first during the preovulatory phase and half being tested first during the postovulatory phase. Again, the most striking finding was the marked stability of individual variations in cardiac reactivity over both time and menstrual cycle phase.

Monitoring protein conformational changes by quenching of intrinsic fluorescence

The quenching of intrinsic fluorescence of human serum albumin and pigeon liver malic enzyme by acrylamide was studied after the proteins were denatured to different stages. The progress of protein denaturation induced by guanidine hydrochloride was accompanied by increasing of effective dynamic quenching constant which provides a convenient parameter for monitoring protein conformational change.

Systemic effects of chronically administered methyl prednisolonate and methyl 17-deoxyprednisolonate

The systemic activities of methyl prednisolonate and methyl 17-deoxyprednisolonate (1) were studied in rats. Methyl 17-deoxyprednisolonate produced significant changes in the amount of sodium ion (decreased) and potassium ion (increased) in urine; however, methyl prednisolonate had no effect on electrolyte balance. Both methyl prednisolonate and methyl 17-deoxyprednisolonate had no effect on liver glycogen content, plasma corticosterone level and relative adrenal weight. In contrast, the parent compound prednisolone caused a significant decrease in liver glycogen content, plasma corticosterone level and relative adrenal weight.

Role of chloride ion as an allosteric activator of angiotensin-converting enzyme

The nature of chloride ion as an activator of angiotensin-converting enzyme was studied by a series of kinetic experiments with hog plasma enzyme preparation. The enzyme required the presence of chloride ion for its full catalytic activity, but its requirement of monovalent anion was not absolute. The KA value for the enzyme-chloride binding was estimated to be about 150 mM in all cases regardless of the peptide substrates employed. In the presence of chloride ion, the activity of the enzyme was increased, but its optimum pH was shifted gradually to the alkaline region up to pH 8.2 depending on the concentration of chloride ion. In addition, in the presence of chloride ion, the apparent Km values were reduced markedly while the Vmax values were not much altered; for example, for the hydrolysis of angiotensin I decapeptide, the Km value decreased by a factor of 50 while only an 18% increase in Vmax was observed when the enzyme was saturated with chloride ion. The result suggests that chloride ion acts as a conformational modifier inducing the affinity of synergistic binding of substrate.

Systemic activities of a new anti-inflammatory steroid: methyl 20-dihydroprednisolonate

The systemic activities of methyl 20-dihydroprednisolonate (1), a new local anti-inflammatory steroid synthesized by modifying the 17 beta-ketol side-chain of prednisolone, on pituitary-adrenal function and liver glycogen content were investigated in rats. The parent compound, prednisolone, administered intramuscularly, caused a significant dose-related decrease in plasma levels of corticosterone, adrenocorticotropic hormone (ACTH), and liver glycogen content in rats. In contrast, methyl 20-dihydroprednisolonate caused mild PA suppression and liver glycogen depletion only at high doses. The steroid acid ester did not exert glycogenic activity, unlike prednisolone, in the adrenalectomized rats.

Anti-inflammatory steroids without pituitary-adrenal suppression

When two new steroids, methyl prednisolonate and methyl 20-dihydroprednisolonate, were applied locally their anti-inflammatory activities were nearly equivalent to those of the parent compound prednisolone in the cotton pellet granuloma bioassay. However, when these two derivatives were administered systemically, their anti-inflammatory activities were weaker than those of the parent compound. Furthermore, unlike the parent compound, these new anti-inflammatory steroids did not suppress pituitary-adrenal function or cause liver glycogen depletion in rats.

Stabilization of rat liver lysosomes by new anti-inflammatory steroids in vitro

Steroid acid esters, synthesized by modifying the 17-ketol side chain of prednisolone, were tested for their in vitro ability to stabilize heavy mitochondrial lysosomes prepared from rat liver. Membrane stabilization was determined by assessing capability of steroids to decrease extrusion of the marker enzymes (acid phosphatase, beta-glucuronidase and aryl sulfatase) from lysosomes incubated in hypo-osmotic sucrose-Tris acetate buffer. Results indicated that prednisolone (1) significantly inhibited the lysosomal release of acid phosphatase as did the new anti-inflammatory steroid, methyl 20-dihydroprednisolonate. Methyl prednisolonate exhibited weak membrane stabilization capacities and 20-dihydroprednisolonic acid, a metabolic product of methyl 20-dihydroprednisolonate, showed virtually no membrane stabilization.