Biomedical subjects

M Maniar

Publications and source records attributed to M Maniar.

8 recordsLinked to original sources

PubMed2001

A fluorescence-based homogeneous assay for measuring activity of UDP-3-O-(R-3-hydroxymyristoyl)-N-acetylglucosamine deacetylase.

UDP-3-O-(R-3-hydroxymyristoyl)-N-acetylglucosamine deacetylase (LpxC) is one of the key enzymes of bacterial lipid A biosynthesis, catalyzing the removal of the N-acetyl group of UDP-3-O-(R-3-hydroxymyristoyl)-N-acetylglucosamine. The lpxC gene is essential in Gram-negative bacteria but absent from mammalian genomes, making it an attractive target for antibacterial drug discovery. Current assay methods for LpxC are not suitable for high throughput screening, since they require multiple product separation steps and the use of radioactively labeled material that is difficult to prepare. A homogeneous fluorescence-based assay was developed that uses UDP-3-O-(N-hexyl-propionamide)-N-acetylglucosamine as a surrogate substrate. This surrogate can be prepared from commercially available UDP-GlcNAc by enzymatic conversion to UDP-MurNAc, which is then chemically coupled to n-hexylamine. Following the LpxC reaction, the free amine of the deacetylation product can be derivatized by fluorescamine, thus generating a fluorescent signal. This surrogate substrate has a K(m) of 367 microM and k(cat) of 0.36 s(-1), compared to 2 microM and 1.5 s(-1) for the natural substrate. Since no separation is needed, the assay is easily adaptable to high throughput screening. IC(50)s of LpxC inhibitors determined using this assay method is similar to those measured by traditional method with the natural substrate.

Amidohydrolases↗

PubMed2001

Resistance of Streptococcus pneumoniae to deformylase inhibitors is due to mutations in defB.

Resistance to peptide deformylase inhibitors in Escherichia coli or Staphylococcus aureus is due to inactivation of transformylase activity. Knockout experiments in Streptococcus pneumoniae R6x indicate that the transformylase (fmt) and deformylase (defB) genes are essential and that a def paralog (defA) is not. Actinonin-resistant mutants of S. pneumoniae ATCC 49619 harbor mutations in defB but not in fmt. Reintroduction of the mutated defB gene into wild-type S. pneumoniae R6x recreates the resistance phenotype. The altered enzyme displays decreased sensitivity to actinonin.

Amidohydrolases↗

PubMed1999

Regulation of the alpha-galactosidase activity in Streptococcus pneumoniae: characterization of the raffinose utilization system.

A 10.2-kb gene region was identified in the Streptococcus pneumoniae genome sequence that contains eight genes involved in regulation and metabolism of raffinose. The genes rafR and rafS are transcribed as one operon, and their gene products regulate the raffinose-dependent stimulation of a divergently transcribed second promoter (P(A)) directing the expression of aga, the structural gene for alpha-galactosidase. Raffinose-mediated transcription from P(A) results in a 500-fold increase in alpha-galactosidase activity in the cell. A third promoter within the cluster is responsible for the transcription of the remaining five genes (rafE, rafF, rafG, gtfA, and rafX), whose gene products might be involved in transport and metabolism of raffinose. The presence of additional internal promoters cannot be excluded. The aga promoter P(A) is negatively regulated by the presence of sucrose in the growth medium. Consistent with catabolite repression (CR), a DNA sequence with high homology to the CRE (cis-active element) was identified upstream of the aga promoter. Sucrose-mediated CR depends on the phosphoenolpyruvate: sucrose phosphotransferase system (PTS) but is unaffected by a mutation in a gene encoding a homolog of the CRE regulatory protein CcpA.

5' Untranslated Regions↗

PubMed1998

Biodegradable polyanhydride devices of cefazolin sodium, bupivacaine, and taxol for local drug delivery: preparation, and kinetics and mechanism of in vitro release.

The overall objective was to design and evaluate biodegradable implants for local drug delivery in clinical conditions and/or diseases described below, which are currently treated with systemic administration of drugs. Local delivery of cefazolin is desired in conditions such as osteomyelitis, soft-tissue infection and for prevention of post-surgical infections. Similarly, implanting a biodegradable device loaded with taxol in the cavity created by tumor resection will provide high local concentrations of taxol killing the malignant cells which may have survived the surgery, thus preventing metastasis and regrowth of the tumor and also prevent the systemic side effects of taxol. Prolonged reversible nerve blockade required in a number of clinical situations involving acute or chronic pain such as post-surgical pain following herniorrhaphy and thoracotomy can be achieved with local delivery of bupivacaine. Therefore, disk-shaped implants of polyanhydride, P(FAD-SA, 50:50 w/w), loaded with 10% w/w of cefazolin sodium, taxol and bupivacaine were prepared and evaluated for content uniformity and in vitro release characteristics for the above mentioned local drug delivery applications. All of cefazolin sodium was released in 14 days while 90% bupivacaine was released in 35 days. In striking contrast, taxol was released very slowly, and only 15% taxol was released in 77 days. The overall release appeared to be following first order kinetics, and the initial linear profile was fitted to zero order kinetics to obtain release parameters. Since cefazolin is highly water soluble and bupivacaine is moderately water soluble, compared to taxol which is extremely lipophilic, the aqueous solubility of the incorporated drug appeared to influence in release characteristics. Very good correlation was observed between release parameters (Ao, ko) and the solubility and intrinsic dissolution rate (IDR) of drugs suggesting that the hydrophilic/hydrophobic nature of the drug influences its release from polyanhydride devices. Since polyanhydrides are believed to undergo pure surface erosion, release of the incorporated drug should be independent of its physicochemical properties, however the results presented in this study suggest otherwise. Therefore, P(FAD-SA, 50:50 w/w) may not be undergoing surface erosion, and the diffusion and dissolution properties of the drug in addition to erosion characteristics of the polyanhydride appear to play a role in drug release. Implants prepared and evaluated in this study released cefazolin, bupivacaine and taxol for a prolonged duration of time; however, depending upon the desired duration of release, an appropriate polyanhydride will have to be selected. For example, taxol was released so slowly that a more hydrophilic polyanhydride may have to be selected to release all the drug in a shorter period of time to be of any therapeutic use. Cefazolin implants released the drug for a sufficient duration for osteomyelitis and soft-tissue infection but the release was more prolonged than required for prevention of post-surgical wound infection.

Anesthetics, Local↗

PubMed1995

Insect repellent formulations of N,N-diethyl-m-toluamide (deet) in a liposphere system: efficacy and skin uptake.

Novel formulations for a deet in liposphere microdispersion in the form of lotion were prepared from natural solid triglycerides and phospholipids dispersed in buffer solution. The formulations containing 6.5, 10, and 20% deet were effective as a repellent against the common aggressive biting mosquitoes, Aedes aegypti and Anopheles stephensi, for up to 6 h. The acute dermal absorption of the 10% loaded formulation was conducted in rabbits using 14C-labeled deet. 14C-labeled deet, 10% in alcohol solution or in liposphere microdispersion was applied to the intact rabbit skin under a porous nonirritating cover for 7 days. Plasma levels of radioactivity were determined for 24 h, and daily for a total of 7 days. The 14C-deet blood levels following intravenous bolus administration were also measured. The bioavailability of deet from 10% ethanol solution was 45%, whereas the bioavailability of deet from lipospheres was 16%, a 3-fold reduction in the amount of deet absorbed. Examination of the rabbits during the experiment and after necropsy showed no evidence of toxicity or irritation. The 10% deet-liposphere formulation was stable at room temperature for at least 1 year.

Aedes↗

PubMed1992

Anesthetic activity of the lipospheres bupivacaine delivery system in the rat.

The Lipospheres Bupivacaine Delivery System (bupivacaine-lipospheres) is a novel sustained-release local anesthetic preparation that has recently been made available for research purposes. This investigation compared the local anesthetic efficacy and safety of 2% bupivacaine-lipospheres, 0.5% bupivacaine plus 1:200,000 epinephrine, lipospheres plain, and physiologic saline following subcutaneous tail injection in the rat. A modified tail-flick paradigm was used to assess local anesthetic efficacy. Animals treated with 2% bupivacaine-lipospheres or 0.5% bupivacaine with epinephrine displayed significant antinociception (P < 0.05) compared to saline or lipospheres plain with 5 min of injection. Bupivacaine with epinephrine had an anesthetic duration of 30 min, whereas 2% bupivacaine-lipospheres had a duration of 3 hr. The local anesthetic blockade produced by both active solutions was completely reversible. All animals gained weight normally during the 1-wk course of the study, and there were no signs of local tissue toxicity at the injection sites. We conclude that 2% bupivacaine-lipospheres is a safe and efficacious local anesthetic preparation in this particular animal model. It possesses an onset of action that is a rapid as 0.5% bupivacaine with 1:200,000 epinephrine, and a duration that is six times longer.

Analysis of Variance↗

PubMed1991

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.

Animals↗

PubMed1990

Polyanhydrides. V. Branched polyanhydrides.

The objective of the present study was to investigate the properties of branched polyanhydrides and compare them to the corresponding linear polymers. Sebacic acid was polymerized with 1,3,5 benzenetricarboxylic acid and poly(acrylic acid) to yield random and graft-type branched polyanhydrides. The polymerization was followed until the gel point and the resulting polymers were evaluated for their physico-chemical properties and degradation behaviour. Drug release from these polymers was studied using morphine as a model drug. The experiment showed that the molecular weights of branched polyanhydride were significantly higher (mol wt 250,000) than the molecular weight of linear poly(sebacic anhydride) (mol wt 80,000). In the case of poly(acrylic acid) branched polymers, the molecular weight increased linearly with increasing concentration of poly(acrylic acid). The specific viscosities of the branched polyanhydrides were lower than linear polyanhydrides with similar molecular weights. Except for the difference in molecular weights, there were no noticeable changes in the physico-chemical or thermal properties of the branched polymers and the linear poly(sebacic anhydride). The degradation of the branched polyanhydride was triphasic and the degradation rates were faster than for linear poly(sebacic anhydride). The release of morphine from the branched polymers was lower than the corresponding poly(sebacic anhydride). Release of morphine was much higher from the poly(acrylic acid) branched polymers compared to the 1,3,5 benzenetricarboxylic acid branched polymers and increased with increasing concentrations of the branching agent. However, in both cases the release rates and the total amounts of morphine released approached that of poly(sebacic anhydride).

Anhydrides↗