Biomedical subjects
Publications and source records attributed to B Mishra.
The case of a patient who developed fungal valve endocarditis due to Candida albicans following balloon mitral valvotomy is presented. The patient did not have any obvious predisposing factors which led to the development of fungal endocarditis.
We have constructed NheI and XhoI optical maps of Escherichia coli O157:H7 solely from genomic DNA molecules to provide a uniquely valuable scaffold for contig closure and sequence validation. E. coli O157:H7 is a common pathogen found in contaminated food and water. Our approach obviated the need for the analysis of clones, PCR products, and hybridizations, because maps were constructed from ensembles of single DNA molecules. Shotgun sequencing of bacterial genomes remains labor-intensive, despite advances in sequencing technology. This is partly due to manual intervention required during the last stages of finishing. The applicability of optical mapping to this problem was enhanced by advances in machine vision techniques that improved mapping throughput and created a path to full automation of mapping. Comparisons were made between maps and sequence data that characterized sequence gaps and guided nascent assemblies.
Bioadhesive chitosan microspheres (Ms) of pentazocine (Pz) for intranasal systemic delivery were prepared with the aim of avoiding the first pass effect, and thus improving the bioavailability and achieving sustained and controlled blood level profiles, as an alternative therapy to injection and to obtain improved therapeutic efficacy in the treatment of chronic pain such as cancer, trauma and post-operative pain, etc. The formulation variables were drug loading, polymer concentration, stirring rate during crosslinking and oils. The microspheres (Ms) were subjected to evaluation for physical characteristics, such as particle size, incorporation efficiency, swelling ability, in vitro bioadhesion, in vitro drug release characteristics and in vivo performance in rabbits. Application of in vitro data to various kinetic equations indicated matrix diffusion controlled drug delivery from chitosan Ms. Drug loading, polymer concentration and stirring speed influenced the drug release profiles significantly while oils had negligible effect. In vivo studies indicated significantly improved bioavailability of Pz from Ms with sustained and controlled blood level profiles as compared to i.v., oral and nasal administration of drug solution. Good correlation was observed between in vitro and in vivo data.
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A case of brain abscess due to Xylohypha bantiana without any obvious predisposing factors and with the uncommon clinical feature of seizures is presented.
It is advantageous to deliver some drugs with short half-life, and which are to be given frequently for chronic ailments, in the form of controlled-release (CR) formulations. The orally administered drugs, in the form of conventional matrix or reservoir type formulations, pose problems of bioavailability fluctuations due to gastric pH variations. Moreover, the release of drug(s) from these systems is affected by the hydrodynamic conditions of the body. Osmotically controlled drug delivery systems utilize the principles of osmotic pressure for the controlled delivery of active agent(s). The release rate of drug(s) from these systems is independent of the physiological factors of the gastrointestinal (GI) tract to a large extent. In the present review, theory underlying the delivery of drugs from osmotic systems is presented. Different types of oral osmotic systems, their advantages over conventional matrix and reservoir types of systems, and their applications are also discussed. Finally, some of the limitations, adverse effects, and patent and market status of these systems are reviewed. These systems form a major segment of drug delivery products. Because of their advantages and strong market potential, it appears that the future of osmotic systems in rate-controlled oral drug delivery is promising.
The accurate mapping of clones derived from genomic regions containing complex arrangements of repeated elements presents special problems for DNA sequencers. Recent advances in the automation of optical mapping have enabled us to map a set of 16 BAC clones derived from the DAZ locus of the human Y chromosome long arm, a locus in which the entire DAZ gene as well as subsections within the gene copies have been duplicated. High-resolution optical mapping employing seven enzymes places these clones into two contigs representing four distinct copies of the DAZ gene and highlights a number of differences between individual copies of DAZ.
In this work, we explore the use of representations in conjunction with DNA microarray technology to measure gene copy number changes in cancer. We demonstrate that arrays of DNA probes derived from low-complexity representations can be used to detect amplifications, deletions, and polymorphic differences when hybridized to representations of genomic DNA. The method is both reproducible and verifiable, and is applicable even to microscopic amounts of primary tumors. We also present a mathematical model for array performance that is useful for designing and understanding DNA microarray hybridization protocols. The future applications and challenges of this approach are discussed.
Man's observation of animals as objects of study undoubtedly began in prehistoric times. The first recorded attempt involving the use of live animals for research was by Ersistratis in Alexandria in 300 B.C. Animal investigation has clearly made possible the enormous advances in drug development in this century. A cursory review of any modern text book of pharmacology or medicine will attest the many drugs currently available to benefit mankind in the struggle to eradicate and control diseases. The main purpose of this article is to describe some of the experimental work on animals which contributed to the discovery and development of drugs benefiting human beings and other animal species. Since animal experimentation has occupied a focal position in all the research leading to useful drugs, one will appreciate that it will be necessary to limit the discussion to certain aspects of this broad and interesting topic. With this in mind, an attempt is made to relate briefly the nature of animal investigations which were instrumental in the development of major classes of drugs. Some attention has also been focused on legislation's on animal experimentation of some developed countries with emphasis on India and to views on animal experimentation. We hope this article will stimulate the minds of the scientists for a rational debate on the future of animal experimentation.
This study was conducted to assess the bacterial flora carried on stethoscopes used by medical personnel and to study the effect of disinfection of stethoscopes on the flora. In the 106 stethoscopes sampled, Gram-positive organisms were the most (60%) frequently isolated. Among them, Staphylococcus aureus accounted for 15.8% of the flora of which 21% were resistant to methicillin. The rate of isolation of S aureus and methicillin resistant S aureus (MRSA) was higher in critical care units. Disinfection was found to significantly reduce the bacterial count.
The ability of the Vitek Yeast Biochemical Card to identify yeast isolates was compared with conventional methods. Of the fifty yeast isolates tested same species identification was obtained in thirty-four isolates. The Vitek yeast biochemical card identified 13 isolates which could not be identified by the conventional tests. Though the Vitek Yeast biochemical card gave a good rapid identification the high cost of each test severely limits its routine use in most of the laboratories.
A whole-genome restriction map of Deinococcus radiodurans, a radiation-resistant bacterium able to survive up to 15,000 grays of ionizing radiation, was constructed without using DNA libraries, the polymerase chain reaction, or electrophoresis. Very large, randomly sheared, genomic DNA fragments were used to construct maps from individual DNA molecules that were assembled into two circular overlapping maps (2.6 and 0.415 megabases), without gaps. A third smaller chromosome (176 kilobases) was identified and characterized. Aberrant nonlinear DNA structures that may define chromosome structure and organization, as well as intermediates in DNA repair, were directly visualized by optical mapping techniques after gamma irradiation.
beta-spectrins are crucial for the maintenance of cell shape, the establishment of cell polarity, and the formation of distinct membrane domains. Our strategy for identifying genes important for hepatocyte polarity has been to utilize subtractive hybridization of early embryonic mouse cDNA liver libraries. As a result, we have cloned three isoforms of a novel beta-spectrin elf (embryonic liver beta-fodrin), and here we report the analysis of elf3, the longest isoform (8172 nt). ELF3 comprises 2154 residues with an overall similarity of 89.0% and 95.3% to mouse beta-spectrin (betaSpIIsigma1) at the nucleotide and amino acid level, respectively. ELF3 is characterized by an actin-binding domain, a long repeat domain, and a short regulatory domain remarkable for the absence of a PH domain. Linkage analysis reveals that elf3 maps to mouse chromosome 11 between D11Bir6 and D11Xrf477, a different chromosomal locus from that of the other four spectrin genes. Northern blot analysis utilizing an elf3 3'-UTR probe demonstrates an abundant 9.0-kb transcript in brain, liver, and heart tissues. Western blot with a polyclonal antibody against ELF identifies a 200 kD protein in mouse liver, brain, kidney, and heart tissues. Immunohistochemical studies demonstrate ELF labeling of the basolateral or sinusoidal membranes surface as well as a granular cytoplasmic pattern in hepatocytes. Antisense studies utilizing cultured liver explants show a vital role of elf3 in hepatocyte differentiation and intrahepatic bile duct formation. The differential expression, tissue localization, and functional studies demonstrate the importance of elf3 in modulating interactions between various components of the cytoskeleton proteins controlling liver and bile duct development.
The aim of our study was to isolate novel gene(s) involved in cell differentiation and embryonic liver development. Mouse cded/lior was identified from subtraction hybridization of embryonic liver cDNA libraries as well as an adult mouse liver genomic DNA library. The full open reading frame of cded/lior encodes a 131-amino acid protein with 71.88% overall similarity to the PH domain of rat PLC-gamma1. A gapped search with the C-terminal region of CDED/LIOR revealed a 36-41% similarity to several proteins related to signal transduction and cell replication, such as ORC1 and KSR. Northern blot analysis of adult mouse tissues shows a strong 2.6-kb transcript restricted to heart and skeletal muscle. RT-PCR utilizing cded/lior-specific primers demonstrates cded/lior mRNAs in heart, brain, and liver tissue throughout mid-embryonic mouse gestation. cded/lior maps to the distal end of mouse Chromosome (Chr) 2. Analysis of the genomic structure for cded/lior demonstrated a single exon gene that is not an alternatively spliced isoform of PLC-gamma1. Analysis of the cded/lior promoter region revealed a high GC-content, high ratio of CpG/GpC, multiple GC-boxes, the lack of a TATA box, CTF/NFI element, and two MyoD-MCK binding sites. These characteristics are also found in several genes important in the regulation of cell growth or DNA synthesis, such as transforming growth factor-beta1, c-Ha-ras, nerve growth factor, epidermal growth factor receptor, and DNA polymerase beta. These results suggest that cded/lior is a mesoderm/muscle-specific transcript that may be involved in the mesodermal inductive and regulatory interactions required for liver formation and embryonic development.
Optical mapping is an approach for the rapid, automated, non-electrophoretic construction of ordered restriction maps of DNA from ensembles of single molecules. Previously, we used optical mapping to make high-resolution maps of large insert clones such as bacterial artificial chromosomes (BAC) and large genomic DNA molecules. Here, we describe a combination of optical mapping and long-range polymerase chain reaction (PCR), in a process we term optical PCR, which enables automated construction of ordered restriction maps of long-range PCR products spanning human genomic loci. Specifically, we amplified three long PCR products, each averaging 14.6 kb in length, which span the 37-kb human tissue plasminogen activator (TPA) gene. PCR products were surface mounted in gridded arrays, and samples were mapped in parallel with either ScaI, XmnI, HpaI, ClaI, or BglII. A contig of overlapping high-resolution maps was generated, which agreed closely with maps predicted from sequence data. The data demonstrate an approach to construct physical maps of genomic loci where very little prior sequence information exists, since the only sequence needed is that required to anchor PCR primers. Large segments of genomic DNA (within the practical limits imposed by long-range PCR) can be mapped quickly and to high resolution without the use of cloning vectors.
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Physical mapping has been rediscovered as an important component of large-scale sequencing projects. Restriction maps provide landmark sequences at defined intervals, and high-resolution restriction maps can be assembled from ensembles of single molecules by optical means. Such optical maps can be constructed from both large-insert clones and genomic DNA, and are used as a scaffold for accurately aligning sequence contigs generated by shotgun sequencing.
The unicellular parasite Plasmodium falciparum is the cause of human malaria, resulting in 1.7-2.5 million deaths each year. To develop new means to treat or prevent malaria, the Malaria Genome Consortium was formed to sequence and annotate the entire 24.6-Mb genome. The plan, already underway, is to sequence libraries created from chromosomal DNA separated by pulsed-field gel electrophoresis (PFGE). The AT-rich genome of P. falciparum presents problems in terms of reliable library construction and the relative paucity of dense physical markers or extensive genetic resources. To deal with these problems, we reasoned that a high-resolution, ordered restriction map covering the entire genome could serve as a scaffold for the alignment and verification of sequence contigs developed by members of the consortium. Thus optical mapping was advanced to use simply extracted, unfractionated genomic DNA as its principal substrate. Ordered restriction maps (BamHI and NheI) derived from single molecules were assembled into 14 deep contigs corresponding to the molecular karyotype determined by PFGE (ref. 3).