Effect of fuel preheating on performance, emission and combustion characteristics of a diesel engine fuelled with Vateria indica methyl ester blends at various loads

The present study examines the preheated (95 °C) and unheated (35 °C) Vateria indica methyl ester (VIME) blends by studying the engine performance, combustion, and emission characteristics at various loads. A single-cylinder, TV1 Kirloskar direct injection diesel engine is used to carry out the tests. Biodiesel produced from Dhupa fat through the transesterification process is used as a renewable fuel in a diesel engine. In this work, diesel (B0), VIME (B100), and two binary blends (B30 and B50) are used. VIME has a higher viscosity, higher density, and lower calorific value than diesel, resulting in lesser brake thermal efficiency (BTE) and higher brake specific energy consumption (BSEC). Due to high viscosity of the biodiesel, preheating of fuel is done before injecting into cylinder. Preheating reduces the viscosity, and enhances the atomization and vaporization of fuel, resulting in improved engine performance. For a given blend of VIME biodiesel and diesel, the preheated blend has better BTE, decreased BSEC and lesser CO and HC emissions, with a slight increment in NO_X emission compared to the unheated blend. The preheated B30 blend has a BTE value of 30.3% which is close to the BTE value of 30.1% of unheated diesel at 100% load condition. CO, HC, and soot emissions are decreased by 16.2%, 34.4%, and 16.5%, respectively, for preheated B100 fuel compared to unheated B100, at full load.

CMAC Trained Optimum Mid course Guidance for Tactical Flight Vehicle

This paper discusses design and validation of neural network based mid-course guidance law of a surface to air flight vehicle. In present study, initially different optimal trajectories have been generated off-line of different pursuer-evader engagements by ensuring minimum flight time, maximum terminal velocity and favorable handing over conditions for seeker based terminal guidance. These optimal trajectories have been evolved by nonlinear programming based direct method of optimisation. The kinematic information of both pursuer and evader, generated based on these trajectories have been used to train cerebellar model articulate controller (CMAC) neural network. Later for a given engagement scenario an on-line near optimal mid-course guidance law has been evolved based on output of trained network. Training has been carried out by CMAC type supervisory neural network. The tested engagement condition is within input/output training space of neural network. Seeker based homing guidance has been used for terminal phase. Complete methodology has been validated along pitch plane of pursuer-evader engagement. During mid-course phase, the guidance demand has been tracked by attitude hold autopilot and during terminal phase, the guidance demanded lateral acceleration has been tracked by acceleration autopilot. System robustness has been studied in presence of plant parameter variations and sensor noise under Monte Carlo Platform.

Histoid Leprosy Presenting with Keloid Like Lesions

A 42 year old male presented with multiple, discrete, hyperpigmented, firm, non elastic, non tender papules and plaques on the posterior trunk of 5 months duration, resembling keloid. The patient had also a few skin colored papules on the anterior trunk and face. The sensations over the skin lesions were intact. The patient had glove and stocking type of anesthesia and bilaterally thickened, non tender peripheral nerve trunks. The slit skin smear for acid fast bacilli from the ear lobes, skin lesions and normal skin were highly positive for Mycobacterium leprae. A skin biopsy showed a well defined collection of spindle shaped histiocytes in the dermis packed with acid fast bacilli. We are presenting here a case of histoid leprosy presenting with keloid like lesions, probably the rarest presentation of histoid leprosy.

Characterization of Vibrio fluvialis qnrVC5 Gene in Native and Heterologous Hosts: Synergy of qnrVC5 with other Determinants in Conferring Quinolone Resistance

Resistance of various pathogens toward quinolones has emerged as a serious threat to combat infections. Analysis of plethora of genes and resistance mechanisms associated with quinolone resistance reveals chromosome-borne and transferable determinants. qnr genes have been found to be responsible for transferable quinolone resistance. In the present work, a new allele qnrVC5 earlier reported in Vibrio fluvialis from this laboratory was characterized in detail for its sequence, genetic context and propensity to decrease the susceptibility for quinolones. The study has revealed persistence of qnrVC5 in clinical isolates of V. fluvialis from Kolkata region through the years 2002–2006. qnrVC5 existed in the form of a gene cassette with the open reading frame being flanked by an upstream promoter and a downstream V. cholerae repeat region suggestive of its superintegron origin. Sequence analysis of different qnrVC alleles showed that qnrVC5 was closely related to qnrVC2 and qnrVC4 and these alleles were associated with V. cholerae repeats. In contrast, qnrVC1, qnrVC3, and qnrVC6 belonging to another group were associated with V. parahaemolyticus repeats. The gene manifested its activity in native V. fluvialis host as well as in Escherichia coli transformants harboring it by elevating the MIC toward various quinolones by twofold to eightfold. In combination with other quinolone resistance factors such as topoisomerase mutations and aac(6’)-Ib-cr gene, qnrVC5 gene product contributed toward higher quinolone resistance displayed by V. fluvialis isolates. Silencing of the gene using antisense peptide nucleic acid sensitized the V. fluvialis parent isolates toward ciprofloxacin. Recombinant QnrVC5 vividly demonstrated its role in conferring quinolone resistance. qnrVC5 gene, its synergistic effect and global dissemination should be perceived as a menace for quinolone-based therapies.

Effect of Carbon Substrates on Rock Phosphate Solubilization by Bacteria from Composts and Macrofauna

Five of the 207 isolates from different composts, farm waste compost (FWC), rice straw compost (RSC), Gliricidia vermicompost (GVC), and macrofauna, showed rock phosphate (RP) solubilization in buffered medium in plate culture. When tested in RP broth medium, all five strains, Enterobacter cloacae EB 27, Serratia marcescens EB 67, Serratia sp. EB 75, Pseudomonas sp. CDB 35, and Pseudomonas sp. BWB 21, showed gluconic acid production and solubilized RP. Based on cellulose-degrading and P-solubilizing ability, two strains were selected for further studies. In the presence of different carbon sources, both strains showed a drop in pH and solubilized RP. P released was maximum with glucose (1212 and 522 micromol) and minimum with cellobiose (455 and 306 micromol) by S. marcescens EB 67 and Pseudomonas sp. CDB 35, respectively. Glucose dehydrogenase (GDH) activity was 63 and 77% with galactose and 35 and 46% with cellobiose when compared to glucose (100%) by EB 67 and CDB 35, respectively. Both strains solubilized RP in the presence of different crop residues. EB 67 and CDB 35 showed maximum cellulase activity (0.027 units) in the presence of rice straw and a mixture of rice straw and root. P solubilized from RP in the presence of pigeonpea root was 134 and 140 micromol with EB 67 and CDB 35. Significantly, these bacteria isolated from composts and macrofauna solubilized rock phosphate in the presence of various pure carbon substrates and crop residues and their importance in soil/rhizosphere conditions is discussed.

Role of drug metabolism in drug discovery and development

Metabolism by the host organism is one of the most important determinants of the pharmacokinetic profile of a drug. High metabolic lability usually leads to poor bioavailability and high clearance. Formation of active or toxic metabolites will have an impact on the pharmacological and toxicological outcomes. There is also potential for drug-drug interactions with coadministered drugs due to inhibition and/or induction of drug metabolism pathways. Hence, optimization of the metabolic liability and drug-drug interaction potential of the new chemical entities are some of the most important steps during the drug discovery process. The rate and site(s) of metabolism of new chemical entities by drug metabolizing enzymes are amenable to modulation by appropriate structural changes. Similarly, the potential for drug-drug interactions can also be minimized by appropriate structural modifications to the drug candidate. However, the optimization of the metabolic stability and drug-drug interaction potential during drug discovery stage has been largely by empirical methods and by trial and error. Recently, a lot of effort has been applied to develop predictive methods to aid the optimization process during drug discovery and development. This article reviews the role of drug metabolism in drug discovery and development.

Potent inhibition of the cytochrome P-450 3A-mediated human liver microsomal metabolism of a novel HIV protease inhibitor by ritonavir: A positive drug-drug interaction

ABT-378 is a potent in vitro inhibitor of the HIV protease and is currently being developed for coadministration with another HIV protease inhibitor, ritonavir, as an oral therapeutic treatment for HIV infection. In the present study, the effect of ritonavir, a potent inhibitor of cytochrome P-450 (CYP) 3A, on the in vitro metabolism of ABT-378 was examined. Furthermore, the effect of ABT-378-ritonavir combinations on several CYP-dependent monooxygenase activities in human liver microsomes was also examined. ABT-378 was found to undergo NADPH- and CYP3A4/5-dependent metabolism to three major metabolites, M-1 (4-oxo) and M-3/M-4 (4-hydroxy epimers), as well as several minor oxidative metabolites in human liver microsomes. The mean apparent K(m) and V(max) values for the metabolism of ABT-378 by human liver microsomes were 6.8 +/- 3.6 microM and 9.4 +/- 5.5 nmol of ABT-378 metabolized/mg protein/min, respectively. Ritonavir inhibited human liver microsomal metabolism of ABT-378 potently (K(i) = 0.013 microM). The combination of ABT-378 and ritonavir was much weaker in inhibiting CYP-mediated biotransformations than ritonavir alone, and the inhibitory effect appears to be primarily due to the ritonavir component of the combination. The ABT-378-ritonavir combinations (at 3:1 and 29:1 ratios) inhibited CYP3A (IC(50) = 1.1 and 4.6 microM), albeit less potently than ritonavir (IC(50) = 0.14 microM). Metabolic reactions mediated by CYP1A2, CYP2A6, and CYP2E1 were not affected by the ABT-378-ritonavir combinations. The inhibitory effects of ABT-378-ritonavir combinations on CYP2B6 (IC(50) = >30 microM), CYP2C9 (IC(50) = 13.7 and 23.0 microM), CYP2C19 (IC(50) = 28.7 and 38.0 microM), and CYP2D6 (IC(50) = 13.5 and 29.0 microM) were marginal and are not likely to produce clinically significant drug-drug interactions.

Phase I and pharmacologic study of a 3-hour infusion of paclitaxel followed by cisplatinum and 5-fluorouracil in patients with advanced solid tumors

A Phase I and pharmacological study of paclitaxel administered as an outpatient, 3-h i.v. infusion just before a 5-day regimen of daily cisplatinum (CP) and a continuous infusion of 5-fluorouracil (5-FU) was performed in patients with advanced solid tumors. A secondary objective was to determine the objective response rate to this regimen. Forty-two patients were enrolled and were evaluable for toxicities. Eighteen patients were previously untreated, whereas the rest had received prior treatment with radiation (J. H. Schiller et al., J. Clin. Oncol., 12: 241-248, 1994), chemotherapy (M. J. Kennedy et al., Clin. Cancer Res., 4: 349-356, 1998), or both modalities (J. H. Schiller et al., J. Clin. Oncol., 12: 241-248, 1994). The paclitaxel dose was escalated from 100-135-170-200-225 to 250 mg/m2, whereas i.v. 5-FU and CP doses were fixed at 1.0 g/m2/day continuous infusion and 20 mg/m2/day, respectively, daily for 5 days. Granulocyte colony-stimulating factor (G-CSF; 5 microg/kg/day) was administered s.c. from day 6, routinely after 250 mg/m2 dose of paclitaxel or after a lower dose of paclitaxel if ANC <500/microl or febrile neutropenia was observed. Patients were treated every 28 days. Plasma and urine samples were collected to determine the pharmacokinetics of paclitaxel. In previously untreated patients, the maximally tolerated dose of paclitaxel in the drug regimen was determined to be 170 mg/m2 without and 250 mg/m2 with G-CSF support. At the higher dose level, mucositis and thrombocytopenia were dose-limiting. In previously treated patients, these toxicities were observed at all dose levels of paclitaxel > or =135 mg/m2. With increasing doses of paclitaxel, a disproportionate increase in the peak concentrations, as well as the area under plasma concentration time-curve, was seen. This nonlinearity was due to saturable total body clearance and volume of distribution of paclitaxel (P < 0.001). The apparent plasma elimination half-life was unaffected by the dose of paclitaxel. CP and 5-FU had no apparent effect on the metabolism of paclitaxel. Among 32 patients evaluable for response, 22 demonstrated an objective response, including five complete remissions. Therefore, a regimen of 3-h infusion of 250 mg/m2 paclitaxel before CP and FU is tolerable with G-CSF (as above) support in previously untreated patients. The regimen also seems to be highly active against breast and esophageal cancers.

In vitro metabolism of the HIV-1 protease inhibitor ABT-378: species comparison and metabolite identification

HIV protease inhibitor ABT-378 (ABT-378) was metabolized very extensively and rapidly by liver microsomes from mouse, rat, dog, monkey, and humans. The rates of NADPH-dependent metabolism of ABT-378 ranged from 2.39 to 9.80 nmol.mg microsomal protein-1.min-1, with monkey liver microsomes exhibiting the highest rates of metabolism. ABT-378 was metabolized to 12 metabolites (M-1 to M-12), which were characterized by mass and NMR spectroscopy. The metabolite profile of ABT-378 in liver microsomes from all five species was similar, except that the mouse liver microsomes did not form M-9, a minor secondary metabolite. The predominant site of metabolism was the cyclic urea moiety of ABT-378. In all five species, the major metabolites were M-1 (4-oxo-ABT-378) and M-3 and M-4 (4-hydroxy-ABT-378). Metabolite M-2 (6-hydroxy-ABT-378) was formed by rodents at a faster rate than by dog, monkey, and human liver microsomes. Metabolites M-5 to M-8 were identified as monohydroxylated derivatives of ABT-378. Metabolites M-9 and M-10 were identified as hydroxylated products of M-1. Metabolites M-11 and M-12 were identified as dihydroxylated derivatives of ABT-378. The metabolite profile in human hepatocytes and liver slices was similar to that of human liver microsomes. The results of the current study indicate that ABT-378 is highly susceptible to oxidative metabolism in vitro, and possibly in vivo, in humans.

ABT-378, a highly potent inhibitor of the human immunodeficiency virus protease

The valine at position 82 (Val 82) in the active site of the human immunodeficiency virus (HIV) protease mutates in response to therapy with the protease inhibitor ritonavir. By using the X-ray crystal structure of the complex of HIV protease and ritonavir, the potent protease inhibitor ABT-378, which has a diminished interaction with Val 82, was designed. ABT-378 potently inhibited wild-type and mutant HIV protease (Ki = 1.3 to 3.6 pM), blocked the replication of laboratory and clinical strains of HIV type 1 (50% effective concentration [EC50], 0.006 to 0.017 microM), and maintained high potency against mutant HIV selected by ritonavir in vivo (EC50, 50-fold after 8 h. In healthy human volunteers, coadministration of a single 400-mg dose of ABT-378 with 50 mg of ritonavir enhanced the area under the concentration curve of ABT-378 in plasma by 77-fold over that observed after dosing with ABT-378 alone, and mean concentrations of ABT-378 exceeded the EC50 for >24 h. These results demonstrate the potential utility of ABT-378 as a therapeutic intervention against AIDS.

Identification of cytochromes P450 involved in the human liver microsomal metabolism of the thromboxane A2 inhibitor seratrodast (ABT-001)

Seratrodast (ABT-001, AA-2414) undergoes cytochrome P450 (CYP)-dependent metabolism to a major (5-methylhydroxy seratrodast; 5-HOS) and a minor 4'-hydroxy seratrodast metabolite in human liver microsomes. The mean apparent K(m) and Vmax for the formation of 5-HOS were 15.5 microM and 589.0 pmol 5-HOS formed/mg protein/min, respectively. Chemical inhibition using isoform-selective CYP inhibitors, correlation of 5-HOS formation with several isoform-specific CYP activities in a panel of liver microsomes, metabolism by microsomes derived from CYP cDNA-expressed B-lymphoblastoid cells, and immunoinhibition by isoform-specific anti-CYP antibodies indicated that 5-HOS formation is catalyzed by CYP3A and CYP2C9/10, with a minor contribution from CYP2C8 and CYP2C19. At clinically relevant concentrations, seratrodast was found to inhibit tolbutamide methylhydroxylation (IC50 = 60 microM), (S)-mephenytoin 4'-hydroxylation (IC50 = 50 microM), and coumarin 7-hydroxylation (IC60 = 95 microM), indicating the potential for significant clinical interactions. The inducers of CYP3A and/or CYP2C9 (e.g. rifampicin and phenytoin) are likely to alter the disposition of seratrodast.

Soft drugs. 21. Design and evaluation of soft analogs of propantheline

The soft drug approach was applied to synthesize seven soft analogs of propantheline, which by design display predictable and controllable decomposition to inactive metabolites. Their synthesis involved the quatemization of several different amine groups with the chloromethyl ester of 9-methylxanthene-9-carboxylic acid. The rates of disappearance were measured for all of the compounds and were found to be more rapid than that of propantheline bromide in a variety of chemical and biological media under in vitro conditions. One of the soft analogs was found to be equipotent with propantheline in an in vitro assay. This soft analog was found to be equipotent with propantheline, in vivo, in protecting the rats against indomethacin-induced gastric ulceration and in inducing mydriasis in rabbits on intravenous administration. The pupil sizes returned faster to predrug levels with the soft analog than with propantheline, indicating increased metabolic lability of the soft analog. The equipotency of this soft analog coupled with increased metabolic lability proves the rationality of the soft drug approach for the design of safer therapeutic agents with higher therapeutic indices.

Cytochrome P450-mediated metabolism of the HIV-1 protease inhibitor ritonavir (ABT-538) in human liver microsomes

The HIV-1 protease inhibitor ritonavir (ABT-538) undergoes cytochrome P450-mediated biotransformation in human liver microsomes to three major metabolites, Ml, M2 and M11, with wide interindividual variation in the rates of metabolite formation. The structures of these metabolites were determined with the use of electrospray ionization mass spectrometry. Chemical inhibition, metabolic correlation, immunoinhibition and metabolism by microsomes derived from specific CYP cDNA-transfected B-lymphoblastoid cell lines indicated that the CYP3A subfamily of enzymes was the major contributor to the formation of M1 and M11, whereas both CYP3A and CYP2D6 contributed to the formation of M2. None of the typical CYP3A substrates/inhibitors (e.g., ketoconazole, troleandomycin) were able to completely inhibit ritonavir metabolism, even at high concentrations. Ritonavir was found to be a potent inhibitor of CYP3A-mediated biotransformations (nifedipine oxidation, IC50) = 0.07 microM; 17alpha-ethynylestradiol 2-hydroxylation, IC50 = 2 microM; terfenadine hydroxylation, IC50 = 0.14 microM). Ritonavir was also found to be an inhibitor of the reactions mediated by CYP2D6 (IC50 = 2.5 microM) and CYP2C9/10 (IC50 = 8.0 microM). The results of this study indicate the potential for in vivo inhibition of the metabolism by ritonavir of drugs that are CYP3A, CYP2D6 and, to a lesser extent, CYP2C9/10 substrates.

Dexamethasone induction of taxol metabolism in the rat

This study examined the effect of dexamethasone (DEX), 100 mg/kg/day for 3 days, on [3H]taxol metabolism in liver microsomes and hepatocytes of male and female Sprague-Dawley rats. In control rats, two isomeric monohydroxylated metabolites, M1 and M2, were formed. The formation of both metabolites was 2-3 times greater in the male than in the female animals. After DEX treatment, M1 increased 2.6-fold in the male animals and 6.5-fold in the female animals. This was accompanied by similar increases in hepatic cytochrome P4503A protein and testosterone 6 beta-hydroxylation. Three additional metabolites (U1, U2, and U3) were formed in the DEX-treated animals only. Isolation of these metabolites from rat hepatocyte incubates by reversed-phase HPLC permitted structure identification of U2 and U3, using tandem MS. The mass spectrum of U3 was consistent with deacetylation of taxol, whereas the mass spectrum of U2 was consistent with deacetylation of the monohydroxylated taxol metabolite M2. A comparison of HPLC and MS data for U3 with those of standard 10-deacetyltaxol suggested that the site of deacetylation might be the 4-position of the taxane ring. Preliminary observations indicate that the deacetylation is caused by a DEX-inducible cytochrome P450.

Taxol metabolism and disposition in cancer patients

The objective of this study was to determine the metabolic fate and disposition of taxol in cancer patients. Five patients received 225 or 250 mg/m2 of taxol together with 100 microCi of [3H]taxol as a 3-hr infusion, followed by cisplatin and 5-fluorouracil. Urine, feces, and blood samples were collected for 120 hr and analyzed for total radioactivity, taxol, and metabolites by reversed-phase HPLC and tandem MS. Total urinary excretion was 14.3 +/- 1.4% (SE) of the dose, with unchanged taxol and an unknown polar metabolite as the main excretion products. Total fecal excretion was 71.1 +/- 8.2%, with 6 alpha-hydroxytaxol being the largest component by far. Unchanged taxol and four other metabolites could also be identified from fecal extracts. The plasma area under the curve for unchanged taxol was 20.5 +/- 2.3 microM.hr and that for total taxol metabolites was 14.2 +/- 4.5 microM.hr. The half-life of total metabolites (5.6 +/- 0.4 hr), however, greatly exceeded that of unchanged taxol (2.9 +/- 0.3 hr). Thus, at 5-hr posttaxol infusion, the plasma concentrations of the five metabolites together exceeded the taxol concentration by 2.4-fold. The findings from this study should be of importance as a guide to further therapeutic evaluation of this drug.

Cytochrome P450 3A-mediated human liver microsomal taxol 6 alpha-hydroxylation

The antitumor drug taxol was metabolized to one major (6 alpha-hydroxytaxol) and two minor metabolites by human liver microsomes. A 10-fold interindividual variability with a Vmax of 1.16 +/- 0.85 nmol/hr/mg of microsomal protein and a Km of 18.0 +/- 12.2 microM was observed for taxol 6 alpha-hydroxylation (mean +/- S.D.; n = 6). The NADPH-dependency and the inhibitory effect of carbon monoxide and piperonyl butoxide on taxol metabolism indicated the involvement of cytochrome P450 (CYP) monooxygenases. Chemical inhibition studies pointed to the CYP 3A subfamily as being responsible for taxol 6 alpha-hydroxylation. However, although some CYP 3A substrates were inhibitory (midazolam, 17 alpha-ethinyl estradiol, quercetin, verapamil and testosterone), others were not (troleandomycin, erythromycin and cyclosporin A). The inhibition was found to be competitive with low Ki values for midazolam (10.5 microM) and 17 alpha-ethinyl estradiol (4.5 microM). Taxol 6 alpha-hydroxylation correlated well with the metabolism of 17 alpha-ethinyl estradiol (r = 0.874; P < .05) and midazolam (r = 0.954; P < .01) in the same livers. Rabbit anti-rat CYP 3A1 antibodies, which cross-react with human CYP 3A isoforms, were inhibitory of taxol 6 alpha-hydroxylation. Although the evidence from these experiments supported the CYP 3A mediation of taxol 6 alpha-hydroxylation, the lack of effect of some inhibitors combined with the inability of a human CYP 3A4 transfected cell line to metabolize taxol point to a CYP 3A isoform other than 3A4. The findings in this study could prove clinically useful for the prediction of potential drug interactions, both inhibitory and inductive of taxol metabolism.

Taxol metabolism in rat hepatocytes

Metabolism of the anticancer drug taxol was investigated in freshly isolated rat hepatocytes. Two main metabolites were separated by reversed-phase HPLC and shown by tandem mass spectrometry to be monohydroxylated metabolites. Kinetic studies revealed apparent Km values of 68 and 61 microM with identical Vmax values for the two metabolites. Verapamil and midazolam, but not phenacetin, showed concentration-dependent inhibition of taxol metabolism with both metabolites being affected equally. The IC50 was about 100 microM for verapamil and 25 microM for midazolam. These observations demonstrate for the first time in vitro metabolism of taxol and suggest that the metabolism may be subject to potentially important interactions with numerous other drugs.

Soft drugs--XVI. Design, evaluation and transdermal penetration of novel soft anticholinergics based on methatropine

Atropine has been reported to produce unwanted systemic side effects on topical administration into the eye. The same problem could arise when atropine is used topically as a suppressant of eccrine sweating. In this study, the principles of soft drug design were applied to methatropine. A hypothetical carboxylate metabolite of methatropine was reactivated by esterification with cyclic and alicyclic alcohols to yield a series of compounds (3a-g). In vitro evaluation by guinea pig ileum assay indicated that the compounds are potent anticholinergics and the lead carboxylate metabolite is about 60 times less potent than the most active compound of the series. The activity was found to decrease with the increasing side chain length. The n-octanol/water partition coefficients were found to be directly dependent on the chain length for the compounds made with straight chain alcohols. The transdermal permeability coefficients across the hairless mice skin were found to be directly dependent on the partition coefficients. The soft drugs are found to metabolize extensively during the penetration process compared to the unmetabolizable nature of methatropine. The soft drugs reported in this study will probably be able to elicit a local action at the site of application but will probably be metabolized rapidly in the systemic circulation, thereby avoiding the systemic side effects with a consequent increase in the therapeutic index.

Soft drugs--XIV. Synthesis and anticholinergic activity of soft phenylsuccinic analogs of methatropine

Three soft drug analogs and a metabolite of methatropine based on phenylsuccinic structural moiety were synthesized and tested for activity. In an in vivo assay, the soft drugs were found to be two orders of magnitude less potent than methatropine while the carboxylate metabolite was found to be one order of magnitude less potent than the soft drugs. A structural isomer of compound 4a was found to be less potent. All the soft drugs tested elicited shorter durations of mydriatic action in rabbit eyes compared to atropine. The untreated eye was dilated in the atropine treated animals while no dilation occurred in the soft drug treated animals indicating facile systemic metabolism of the soft drugs to inactive moieties, possibly the carboxylate metabolite. In in vitro stability studies, the soft drugs have been found to be more hydrolytically labile than atropine. The shorter duration of mydriatic action of compound 4a coupled with increased hydrolytic lability make this a candidate for further study.

Soft drugs 15: mydriatic activity and transcorneal penetration of phenylsuccinic soft analogs of methscopolamine as short acting mydriatics

Soft drug analogs of methscopolamine (4 a-c) were tested for mydriatic activity in rabbits' eyes. After unilateral administration of equieffective doses, the AUC24hrs and the mydriatic recovery times were found to be significantly lower with the soft drugs compared to methscopolamine. At equieffective doses, the AUC24hrs for soft drugs ranged from 22.4% to 60% of that of methscopolamine. Significant dilation of the untreated eye was observed with methscopolamine but not with the soft drugs after unilateral administration. Soft drug 4a exhibited only 10.4% of the AUC6hrs (untreated eye) of that of methscopolamine. Shorter durations of mydriatic action combined with potentially reduced systemic side effects make these compounds candidates for further study. In vitro rabbit transcorneal penetration of soft analog 4a was found to be significantly higher than methscopolamine.

Binding of taxol to human plasma, albumin and alpha 1-acid glycoprotein

The binding of taxol to human plasma and to individual plasma proteins was studied by equilibrium dialysis. Taxol was found to bind extensively (about 95%) without a significant difference between healthy volunteers and cancer patients. At clinically relevant concentrations (0.1-6 microM), the binding was found to be concentration independent, indicating nonspecific hydrophobic binding. Human serum albumin and alpha 1-acid glycoprotein were found to contribute about equally to the binding, with a minor contribution from lipoproteins. None of the drugs commonly coadministered with taxol (dexamethasone, diphenhydramine, ranitidine, doxorubicin, 5-fluorouracil and cisplatin) altered the binding of taxol significantly. The protein binding of taxol was found to dramatically decrease the red blood cell uptake of taxol.

Pixel-based reconstruction (PBR) promising simultaneous techniques for CT reconstructions

Algorithms belonging to the class of pixel-based reconstruction (PBR) algorithms, which are similar to simultaneous iterative reconstruction techniques (SIRTs) for reconstruction of objects from their fan beam projections in X-ray transmission tomography, are discussed. The general logic of these algorithms is discussed. Simulation studies indicate that, contrary to previous results with parallel beam projections, the iterative algebraic algorithms do not diverge when a more logical technique of obtaining the pseudoprojections is used. These simulations were carried out under conditions in which the number of object pixels exceeded (double) the number of detector pixel readings, i.e., the equations were highly underdetermined. The effect of the number of projections on the reconstruction and the convergence (empirical) to the exact solution is shown. For comparison, the reconstructions obtained by convolution backprojection are also given.