Cyclic adenosine monophosphate phosphodiesterase in brain: effect on anxiety.

Drugs that reduce anxiety may be mediated by cyclic adenosine monophosphate in the brain because (i) potent anxiety-reducing drugs are also potent inhibitors of brain phosphodiesterase activity; (ii) dibutyryl cyclic adenosine monophosphate has the ability to reduce anxiety; (iii) the methylxanthines show significant anxiety-reducing effects; (iv) theophylline and chlordiazepoxide produce additive anxiety-reducing activity; and (v) there is a significant correlation between the anxiety-reducing property of drugs and their ability to inhibit phosphodiesterase activity in the brain.

Interstitial chemotherapy of the 9L gliosarcoma: controlled release polymers for drug delivery in the brain.

The administration of drugs directly into the central nervous system using polymers as drug carriers may improve the treatment of malignant brain tumors. In this study, the effect of the interstitial, localized delivery of 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) incorporated into controlled release polymers implanted adjacent to the 9L gliosarcoma was assessed in s.c. and intracranial (i.c.) models. In the s.c. experiment, the 9L gliosarcoma was implanted in the flank of rats and subsequently treated with BCNU either (a) delivered in controlled release polymers inserted adjacent to the tumor or (b) administered systemically by i.p. injections or by controlled release polymers inserted at a site distant from the tumor. The interstitial release of BCNU adjacent to the tumor in the flank resulted in a significant tumor growth delay of 16.3 days, as compared to a growth delay of 9.3 and 11.2 days obtained with the systemic administration of BCNU. In the i.c. experiment, the 9L gliosarcoma was implanted in the brain of Fischer 344 rats and treated either (a) with controlled release polymers containing BCNU inserted into the brain or (b) with the systemic i.p. administration of BCNU. The interstitial release of BCNU in the brain resulted in a significant 5.4- to 7.3-fold increased survival, compared with a 2.4-fold increased survival after the systemic administration of the same dose of BCNU. The two groups with i.c. tumors treated interstitially had 17 and 42% cures, but no long-term cures were obtained in the group treated with systemic therapy. The localized, controlled delivery of chemotherapeutic agents in the s.c. tissues and in the brain via polymeric carriers may be more effective than standard systemic chemotherapy. This approach could be used to deliver a wide variety of agents into the central nervous system to treat diverse neuropathological conditions which remain refractory to systemic therapy.

Drug delivery to the brain using polymers.

The delivery of drugs to the brain has been a major challenge to the scientist developing drugs designed for central nervous system (CNS) activity. One of the obstacles to the progress is the transport of drug through the blood brain barrier (BBB). The criteria for effective drug delivery to the CNS include the following: (a) the drug must have access to the brain, (b) the effect of the drug should be localized, (c) the drug must be stable, and (d) the effective dose should be sustained and controlled. To meet some of the above criteria, two approaches have been used: systemic administration of drugs, and direct delivery of drugs into the brain. The systemic administration of drugs relies on passive diffusion of drug through the BBB, formation of lipid soluble prodrugs and the use of monoclonal antibodies for targeting the drug to the CNS. The other approach includes the use of implantable polymer systems and infusion pumps. Both of the approaches have some advantages and disadvantages. Because of the enormous amount of literature on drug delivery to the brain, the following review focuses on the use of polymer-based implantable systems. The review includes nondegradable and biodegradable polymer implants from the conceptual phase to the clinic.

Correlations of PDE-4 inhibition between enzymes of smooth muscle and inflammatory cell sources.

The sensitivities of PDE-4 enzymes from smooth muscle and inflammatory cell sources from different species to a range of structurally diverse compounds were compared. All inflammatory cell PDE-4 sources displayed good crosscorrelations in their sensitivity to inhibition by these compounds. Similarly, PDE-4 enzymes from smooth muscle sources were well-correlated; however, there was no crosscorrelation between PDE-4 from smooth muscle sources and those of inflammatory cell sources, possibly reflecting differences in subcellular location of enzymes as well as subtype expression. The present study concludes that PDE-4 preparations from smooth muscle sources as well as those from inflammatory cell sources may be used to model the potential smooth muscle cell relaxing properties and anti-inflammatory properties of a compound in relation to human asthma.

Suprofen concentrations in human breast milk.

Six healthy females who had been nursing their infants for 6 to 11 months received a single, 200-mg oral dose of suprofen, an analgesic which has been evaluated clinically. Blood and milk samples were collected at discrete times over an 8-hour period and suprofen concentrations in milk and plasma were determined by HPLC. The binding of suprofen to milk and plasma proteins was determined by equilibrium dialysis. The maximum concentrations of suprofen in the milk ranged from 0.118 to 0.232 microgram/ml and occurred from 1 to 2 hours after dose administration. The maximum plasma suprofen concentrations ranged from 13.8 to 28.3 micrograms/ml and occurred from 0.5 to 2 hours after dosing. Within any subject, the peak suprofen concentration in milk was 0.5 to 0.9 per cent of the peak concentration in plasma. Suprofen was extensively bound to plasma proteins (99.4 per cent) and minimally bound to milk proteins (10 per cent). The average milk/plasma ratio based on area-under-the-curve measurements was approximately 0.014, or 1.4 per cent. This ratio agrees well with an estimated value of 1.2 per cent for the pH-dependent, passive diffusion of suprofen from plasma into milk. From these data, it appears that there would be minimal suprofen exposure to a nursing infant after administration of recommended doses to the nursing mother.

The intracerebral distribution of BCNU delivered by surgically implanted biodegradable polymers.

The local concentration and distribution of 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) within normal brain tissue were studied following surgical implantation of biodegradable polymer containing BCNU in New Zealand White rabbits. Cylindrical discs of poly(bis(p-carboxyphenoxy)-propane:sebacic acid) copolymer in a 20:80 formulation were made containing [3H]-inulin or [3H]-BCNU labeled in the methylene hydrogens of the chloroethyl groups. These were implanted in the brains of 56 New Zealand White rabbits. The animals were sacrificed 3, 7, 14, or 21 days later and the brains were rapidly removed, frozen, and prepared for quantitative autoradiography. Autoradiographs from coronal sections bisecting the polymer were analyzed to determine both the proportion of the brain section exposed to the tracer and the local drug concentrations as a function of distance from the polymer. Tritiated BCNU was also injected directly into the brains of eight additional rabbits, and local brain concentrations were studied over time. The results of this study demonstrate that approximately 50% of the area of the brain sections was exposed to radiolabeled compound 3 days after BCNU-polymer implantation, 15% at 7 days, and less than 10% at 14 and 21 days. Polymer discs containing 600 micrograms BCNU generated 6 mM concentrations of BCNU in brain tissue 10 mm from the polymer at 3 and 7 days. Pharmacological studies demonstrated that approximately 25% of the tritium label was associated with intact BCNU 3 days following polymer implantation. Radiolabeled inulin delivered by polymer remained dispersed throughout the ipsilateral hemisphere for 14 days. Direct injection of [3H]-BCNU into brain parenchyma resulted in widely distributed tracer at 1 and 3 hours with rapid disappearance thereafter. It is concluded that local delivery of BCNU to brain tissue with this polymeric drug delivery system results in sustained high local concentrations of BCNU which may be of value in the treatment of patients with brain tumors.

Heterogeneity of biochemical actions among vasodilators.

Thirty-four vasodilators were screened in several in vitro biochemical assays related to smooth muscle excitation-contraction coupling, binding to beta 1-,beta 2-, and alpha-adrenergic receptors, inhibition of phosphodiesterase activity, and antagonism of calcium accumulation. Isoproterenol and perhexiline only exhibited binding to beta-adrenergic sites. Ergocryptine, tolazoline, and amotriphene only bound to alpha-adrenergic receptors. Leniquinsin, papaverine, proquazone, dioxyline, hoquizil, quazodine, and theophylline were active only as phosphodiesterase inhibitors. Isoxsuprine, nylidrin, and bencyclane bound to alpha- and beta-receptors. Pentoxifylline bound to beta 1-sites and inhibited phosphodiesterase. Cyclandelate bound to beta 2-sites and blocked calcium accumulation. Cinnarizine and flunarizine antagonized calcium accumulation and bound to alpha-sites. Prazosin bound to alpha-sites and inhibited phosphodiesterase. Ethaverine and dipyridamole were inhibitors of phosphodiesterase and calcium accumulation. Nafronyl bound to beta 2- and alpha-sites and antagonized calcium accumulation. Mebeverine bound to beta 2- and alpha-receptors and inhibited phosphodiesterase activity and calcium accumulation. Verapamil bound to alpha-sites, and blocked phosphodiesterase and calcium accumulation. Quinazosin bound to beta 2- and alpha-receptors and antagonized both phosphodiesterase activity and calcium accumulation. Vasodilators that were inactive in all assays included niacin, nicotinyl alcohol, inositol nicotinate, amyl nitrite, sodium nitroprusside, diazoxide, hydralazine, and protoveratrine. Vasodilators should not be considered as a single drug class since they act on various mechanisms related to coupling of neuronal excitation to muscular contractility.

Differential effects of food on the bioavailability of controlled-release oxycodone tablets and immediate-release oxycodone solution.

The effects of a high-fat meal on the bioavailability of oxycodone hydrochloride, administered as a recently developed 40 mg controlled-release (CR) tablet or a 20 mg immediate-release (IR) solution, were evaluated in a randomized crossover study in 22 normal male and female subjects. Serial blood samples were collected for 36 h after dosing and analyzed for oxycodone by a validated method using gas chromatography/mass spectrometry. There was no significant food effect with CR oxycodone as judged by 90% confidence interval (CI) analysis of AUC0-infinity and Cmax values under fed and fasted conditions. For the IR solution, both oxycodone bioavailability and peak plasma oxycodone concentration were significantly altered by consumption of the high-fat meal, with the mean value for AUC0-infinity increasing to 120% (CI = 109-132%) and the mean value for Cmax decreasing to 82% (CI = 47-91%) of values observed in the fasted condition. Adverse events reported for both formulations were mostly mild to moderate in severity and typical of those observed with opioids.

Bone conduction implants: transcutaneous vs. percutaneous.

Clinical experience with transcutaneous bone conduction implants has demonstrated that they are most beneficial for patients with purely conductive hearing loss in at least one ear. Percutaneous bone conduction implants, however, have been reported to provide adequate benefit for patients with mixed hearing loss with bone conduction pure-tone averages up to 45 dB HL (Tjellstrom, 1989). The results of 24 Xomed Audiant osseointegrated bone conduction hearing devices (including a clinical trial on two patients using a new, larger magnet [Neodynium Iron Boron]), plus the results of eleven patients implanted and fitted with the percutaneous bone-anchored hearing aid are reported. Aided results with these devices will be presented. In addition, general comparisons of benefit obtained with the two devices will be made for patients who exhibit similar hearing losses. Finally, a direct comparison will be made on two patients who have undergone both implant procedures.

Lack of steroidogenic response to cyclic AMP and ACTH in adrenal cells from rats bearing the MtTF4 tumor.

Adrenal cell suspensions prepared from rats bearing the MtTF4 tumor failed to increase corticosterone production when exposed to adenosine 3', 5'-cyclic monophosphate (cyclic AMP) or ACTH, placing the defect in these adrenals beyond the ACTH receptor site. Adrenal cells from normal rats responded well to these stimuli. Adrenal cyclic AMP phosphodiesterase prepared from the tumor bearing rats appeared normal both with respect to its specific activity and inhibition profile with theophylline. Exposure of the MtTF4 adrenal cells to 1,2-3H-cholesterol in the presence of either cyclic AMP or ACTH did not result in an increase in radioactively labeled corticosterone, whereas increased label could be demonstrated in adrenal cells from normal rats similarly treated.

A new assay for the measurement of mediator release from rat peritoneal mast cells.

In this report, we describe a new in vitro experimental system for monitoring the release, and inhibition of release, of [3H]-serotonin from rat peritoneal mast cells, which can be used as a novel screen for evaluation of compounds effective in immediate hypersensitivity reactions. This assay is an improvement on existing assays since the cells are not required to be exposed to hormones at any time during the procedure. In this assay, 1 microgram/ml of compound 48/80 consistently produced a 6- to 8-fold-increase in release of serotonin with a low background release of 4-5%. Disodium chromoglycate (DSCG), a standard inhibitor of histamine release, effectively inhibited compound-48/80-stimulated serotonin release with an average I50 of 2.1 X 10(-4) M. Several other potential antiasthmatic agents were far more potent than DSCG.

Dissociation of lipolysis from the levels of cyclic AMP in rat epididymal fat cells.

Two compounds, theophylline and 8-aza-9-furfuryl-adenine (SQ 4665), were found to maximally stimulate lipolysis in preparations of rat epididymal fat cells in the absence of exogenous hormones. Cyclic AMP levels in lipocytes maximally stimulated by either agent alone were unchanged from control levels. In contrast, lipolysis stimulated by either epinephrine alone or in combination with several cyclic nucleotide phosphodiesterase inhibitors correlated well with increases in the levels of cyclic AMP observed. These results suggest the presence of a non-cyclic AMP dependent pathway for the stimulation of lipolysis in rat epididymal fat cells.