PubMed Health⌕ Search

Biomedical subjects

A Sen

Publications and source records attributed to A Sen.

At least 19 recordsLinked to original sources
PubMed2001

Adipogenic potential of human adipose derived stromal cells from multiple donors is heterogeneous.

The current study was done to assess if heterogeneity existed in the degree of adipogenesis in stromal cells (preadipocytes) from multiple donors. In addition to conventional lipid-based methods, we have employed a novel signal amplification technology, known as branched DNA, to monitor expression of an adipocyte specific gene product aP2. The fatty acid binding protein aP2 increases during adipocyte differentiation and is induced by thiazolidinediones and other peroxisome proliferator activated receptor gamma ligands. The current work examined the adipogenic induction of aP2 mRNA levels in human adipose tissue stromal cells derived from 12 patients (mean age +/- SEM, 38.9 +/- 3.1) with mild to moderate obesity (mean body mass index +/- SEM, 27.8 +/- 2.4). Based on branched DNA technology, a rapid and sensitive measure of specific RNAs, the relative aP2 level in adipocytes increased by 679 +/- 93-fold (mean +/- SEM, n=12) compared to preadipocytes. Normalization of the aP2 mRNA levels to the housekeeping gene, glyceraldehyde phosphate dehydrogenase, did not significantly alter the fold induction in a subset of 4 patients (803.6 +/- 197.5 vs 1118.5 +/- 308.1). Independent adipocyte differentiation markers were compared between adipocytes and preadipocytes in parallel studies. Leptin secretion increased by up to three-orders of magnitude while measurements of neutral lipid accumulation by Oil Red O and Nile Red staining increased by 8.5-fold and 8.3-fold, respectively. These results indicate that preadipocytes isolated from multiple donors displayed varying degrees of differentiation in response to an optimal adipogenic stimulus in vitro. This work also demonstrates that branched DNA measurement of aP2 is a rapid and sensitive measure of adipogenesis in human stromal cells. The linear range of this assay extends up to three-orders of magnitude and correlates directly with independent measures of cellular differentiation.

Adipocytes↗
PubMed2001

The evolution of human group B rotaviruses.

The largest reported rotavirus epidemic affected well over a million people in China during 1982-83 and was caused by the adult diarrhoea rotavirus (ADRV), a serogroup B rotavirus. However, ADRV has not been reported outside China since the last recorded small outbreak there in 1987. Here we present evidence that offers an explanation for the sudden appearance and disappearance of the epidemic ADRV strain.

China↗
PubMed2001

Thiazolidinediones and glucocorticoids synergistically induce differentiation of human adipose tissue stromal cells: biochemical, cellular, and molecular analysis.

While adipocyte differentiation has been studied extensively in murine cultures, the lack of a readily available preadipocyte model has hindered equivalent studies in man. We describe methods for the isolation and culture of primary human stromal cells from surgical adipose tissue specimens. In vitro, the stromal cells rapidly differentiate in response to a combination of adipogenic agents. Among these, glucocorticoids and thiazolidinediones act together to induce the formation of lipid vacuoles within the cells. These morphologic changes accompany the increased expression of 2 characteristic adipocyte proteins, the cytoplasmic enzyme glycerol phosphate dehydrogenase (GPDH) and the secreted cytokine leptin. Likewise, stromal cell differentiation results in elevated mRNA levels for the fatty acid binding protein aP2 and the adipogenic regulatory transcription factors CCAAT/enhancer binding protein alpha (C/EBPalpha) and peroxisome proliferator-activated receptor gamma (PPARgamma) in addition to leptin. The in vitro differentiated stromal cells exhibit a lipolytic response to beta-adrenergic agonists, comparable to that reported with primary human adipocytes. These studies demonstrate the validity of human adipose tissue-derived stromal cells as a reliable in vitro model for investigations of adipocyte metabolism in humans.

Adipose Tissue↗
PubMed2000

Structural constraints regulating triple helix formation by A-tracts.

The study concerns the propensity of triple helix formation by different DNA oligonucleotides containing long A-tracts with and without flanking GxC base pairs in order to probe the role of length of the A-tract and the flanking sequences. From nuclear magnetic resonance (NMR) studies of imino proton spectra and circular dichroism (CD) spectroscopy of samples composed of potential triplex forming strand sequences in correct stoichiometries, we have concluded that 8-mer A-tracts flanked by GxC base pairs exert significant steric hindrance to triple helix formation. When as much as 50 mM Mg2+ was added, no triple helix formation was observed in these samples. In contrast, open-ended 8-mer A-tracts formed triplex with the corresponding two T8 strands under relatively mild ionic conditions (100 mM Na+). Moreover, the shorter the length of the A-tract, the less is the hindrance to form a triple helix.

Base Pairing↗
PubMed2000

Experimental evidence of time-delay-induced death in coupled limit-cycle oscillators

Experimental observations of time-delay-induced amplitude death in two coupled nonlinear electronic circuits that are individually capable of exhibiting limit-cycle oscillations are described. The existence of multiply connected death islands in the parameter space of coupling strength and time delay for coupled identical oscillators is established. The existence of such regions was predicted earlier on theoretical grounds [Phys. Rev. Lett. 80, 5109 (1998); Physica (Amsterdam) 129D, 15 (1999)]. The experiments also reveal the occurrence of multiple frequency states, frequency suppression of oscillations with increased time delay, and the onset of both in-phase and antiphase collective oscillations.

Journal Article↗
PubMed2000

Mechanisms underlying olfactory neuronal connectivity in Drosophila-the atonal lineage organizes the periphery while sensory neurons and glia pattern the olfactory lobe.

Patterning of the antennal lobe of adult Drosophila occurs through a complex interaction between sensory neurons, glia, and central neurons of larval and adult origin. Neurons from the olfactory sense organs are organized into distinct fascicles lined by glial cells. The glia originate from one of the three types of sensory lineages-specified by the proneural gene atonal. Gain-of-function as well as loss-of-function analysis validates a role for cells of the Atonal lineage in the ordered fasciculation of sensory neurons. Upon entry of the antennal nerve to central regions, sensory neurons at first remain closely associated with central glia which lie around the periphery of the lobe anlage. Coincident with the arrival of sensory neurons into the brain, glial precursors undergo mitosis and neural precursors expressing Dachshund appear around the lobe. Sensory neurons and glial cells project into the lobe at around the same time and are likely to coordinate the correct localization of different glomeruli. The influence of sensory neurons on the development of the olfactory lobe could serve to match and lock peripheral and central properties important for the generation of olfactory behavior.

Animals↗
PubMed2000

Amplification of various genes of human group B rotavirus from stool specimens by RT-PCR.

BACKGROUND: The detection of the human group B rotavirus (HuGBR) CAL strain from India has given us an opportunity to design suitable primers for the detection of HuGBR since CAL is the second HuGBR detected until now, the Chinese Adult Diarrhoea Rotavirus (ADRV) being the first reported human pathogen belonging to this group of viruses. The primers described here may thus be used for the detection of human group B rotaviruses by reverse transcription-PCR (RT-PCR) in a diagnostic laboratory. OBJECTIVE: To establish a set of primers suitable for the detection of various genes of human group B rotaviruses using a rapid RT-PCR assay. STUDY DESIGN: Until recently, the Chinese ADRV strain was the only HuGBR strain that had been partially sequenced by cloning various viral genes using vector-specific primers. Consequently, there are very few reports in the literature describing primers that may be used for the detection of HuGBR viruses using RT-PCR in a clinical laboratory. The sequences of various genes from the ADRV strain that had been submitted to the nucleotide sequence database GenBank were analyzed in order to design several putative detection primer pairs for an RT-PCR assay. The rationale was to amplify the cognate genes from five isolates of the HuGBR CAL strain (CAL-1 to CAL-5) that have been detected to date from India. Primers that resulted in a specific product of the expected size from the CAL isolates were used to standardize a protocol for amplifying various genes of the CAL isolates under identical reaction conditions. RESULTS: Out of several synthetic oligonucleotides designed, 12 were found to be satisfactory for the amplification of gene segments 4, 5, 6, 7, and 9 from the five CAL isolates and are presented here. A set of previously described primers that have been shown to be specific for human group B rotavirus gene segment 8 were also found to amplify the cognate gene from the CAL isolates. All the reactions were carried out using the same thermal cycling conditions. CONCLUSIONS: The extreme virulence potential of HuGBR has been documented in several epidemics in China. Until recently, the Chinese ADRV strain was the only known HuGBr strain. As there have not been any reports of HuGBR infections outside China, there are no consensus nucleotide sequences available for HuGBR that may be used to validate primers for the detection of HuGBR. Here we report a set of 12 primer sequences that were designed from ADRV sequences and also found to amplify various genes from the different CAL isolates and hence may represent consensus primers suitable for the detection of HuGBR.

DNA Primers↗
PubMed2000

Imino proton exchange in DNA catalyzed by ammonia and trimethylamine: evidence for a secondary long-lived open state of the base pair.

The base-pair opening kinetics of the self-complementary oligomer d(CGCGAATTCGCG)(2) has been derived from NMR measurements of the imino proton exchange. In general, it has previously been found that imino proton exchange in duplex DNA is limited by the proton-transfer step from the open state and that the dependence of the exchange times on the inverse concentration of an added exchange catalyst is linear. In the present study, a curvature is observed for, in particular, the innermost AT base pair with both ammonia and trimethylamine (TMA) as exchange catalysts. The two catalysts act on the same open states, but the accessibility of TMA is reduced by a factor of 2-3 compared to ammonia. Assuming that ammonia accesses the imino proton equally in the open state of the base pair and in the mononucleoside, the curvature is consistent with 7-9% of the openings ending in open states with lifetimes of about 1 micros while the bulk of open-state lifetimes fall in the nanosecond range. A curvature is also found for the exchange times of the imino protons in the A-tract sequence CGCA(8)CGC/GCGT(8)GCG. This curvature becomes increasingly pronounced from the 5'-end toward the center of the tract and hereby seems to be correlated with the contraction of the minor groove. Thus, while the base-pair lifetimes deduced from the present study are in accordance with previous measurements, a substantial fraction of the open states formed by the central AT-base pairs in the two oligomers exhibits microsecond lifetimes in contrast to previous estimates in the nanosecond range. These findings may be of relevance for the way sequence specific recognition is accomplished by proteins and ligands.

Ammonia↗
PubMed2000

Activation of a rel-A/CEBP-beta-related transcription factor heteromer by PGG-glucan in a murine monocytic cell line.

PGG-Glucan is a soluble beta-glucan immunomodulator that enhances a variety of leukocyte microbicidal activities without activating inflammatory cytokines. Although several different cell surface receptors for soluble (and particulate) beta-glucans have been described, the signal transduction pathway(s) used by these soluble ligands have not been elucidated. Previously we reported that PGG-Glucan treatment of mouse BMC2.3 macrophage cells activates a nuclear factor kappa-B-like (NF-kappaB) transcription factor complex containing subunit p65 (rel-A) attached to an unidentified cohort. In this study, we identify the cohort to be a non-rel family member: a CCAAT enhancer-binding protein-beta (C/EBP-beta)-related molecule with an apparent size of 48 kDa, which is a different protein than the previously identified C/EBP-beta p34 also present in these cells. C/EBP-beta is a member of the bZIP family whose members have previously been shown to interact with rel family members. This rel/bZIP heteromer complex activated by PGG-Glucan is different from the p65/p50 rel/rel complex induced in these cells by lipopolysaccharide (LPS). Thus, our data demonstrate that PGG-Glucan uses signal transduction pathways different from those used by LPS, which activates leukocyte microbicidal activities and inflammatory cytokines. We further show that heteromer activation appears to use protein kinase C (PKC) and protein tyrosine kinase (PTK) pathways, but not mitogen-activated protein kinase p38. Inhibitor kappa-B-alpha (IkappaB-alpha) is associated with the heteromer; this association decreases after PGG-Glucan treatment. These data are consistent with a model whereby treatment of BMC2.3 cells with PGG-Glucan activates IkappaB-alpha via PKC and/or PTK pathways, permitting translocation of the rel-A/CEBP-beta heteromer complex to the nucleus and increases its DNA-binding affinity.

Adjuvants, Immunologic↗
PubMed2000

Salivary fistulae.

Three cases of unusual cervical fistulae are presented with a review of the literature to caution against labelling all lateral cervical fistulae as simple branchial fistulae or midline ones as dermoid cysts.

Child↗
PubMed2000

Further immunochemical and biocatalytic characterization of CYP1A1 from feral leaping mullet liver (Liza saliens) microsomes.

CYP1A is known to play important roles in the metabolism, detoxification and bioactivation of carcinogens and other xenobiotics in animals including fish. In our laboratory, CYP1A1 was obtained in a highly purified form with a specific content of 15-17 nmol P450 per mg protein from liver microsomes of feral fish, leaping mullet (Liza saliens). Purified mullet CYP1A1 showed a very high substrate specificities for 7-ethoxyresorufin and 7-methoxyresorufin in a reconstituted system containing purified fish P450 reductase and lipid. In addition, effects of each individual components of the reconstituted system, i.e., CYP1A1 and P450 reductase on 7-methoxyresorufin O-demethylase (MROD) activity were studied. 7-ethoxyresorufin O-deethylase (EROD) activity was strongly inhibited by alpha-naphthoflavone (ANF). At 0.5 and 2.5 microM. ANF inhibited EROD activity by 90 and 98%, respectively. Mullet CYP1A1 did not catalyze monooxygenations of other substrates such as aniline, ethylmorphine, N-nitrosodimethylamine and p-nitrophenol. Antibodies produced against CYP1A1 orthologues in fish such as trout and scup showed strong cross-reactivity with the purified mullet CYP1A1. In addition, anti-L. saliens liver CYP1A1 produced in our laboratory inhibited both the EROD and MROD activities catalyzed by L. saliens liver microsomes but stronger inhibition was observed with EROD activity. On the other hand, anti-mullet CYP1A1 antibodies showed very weak cross-reactivity with two proteins (presumably CYP1A1 and CYP1A2) in 3MC-treated rat liver microsomes. Moreover, 3MC-treated rat liver microsomal EROD activity was weakly inhibited by the anti-L. saliens liver CYP1A1. These results strongly suggested that the purified mullet CYP1A1 is structurally, functionally and immunochemically similar to the CYP1A1 homologues purified from other teleost species but functionally and immunochemically distinct from mammalian CYP1A1.

Animals↗
PubMed2000

Sense organ identity in the Drosophila antenna is specified by the expression of the proneural gene atonal.

We have shown that the basic helix-loop-helix transcription factor Atonal is sufficient for specification of one of the three subsets of olfactory sense organs on the Drosophila antenna. Misexpression of Atonal in all sensory precursors in the antennal disc results in their conversion to coeloconic sensilla. The mechanism by which specific sense organ fate is triggered remains unclear. We have shown that the homeodomain transcription factor Cut which acts in the chordotonal-external sense organ choice does not play a role in olfactory sense organ development. The expression of atonal in specific domains of the antennal disc is regulated by an interplay of the patterning genes, Hedgehog and Wingless, and Drosophila epidermal growth factor receptor pathway.

Animals↗
PubMed2000

A system for determination of 3D vessel tree centerlines from biplane images.

With the increasing number and complexity of therapeutic coronary interventions, there is an increasing need for accurate quantitative measurements. These interventions and measurements may be facilitated by accurate and reproducible magnifications and orientations of the vessel structures, specifically by accurate 3D vascular tree centerlines. A number of methods have been proposed to calculate 3D vascular tree centerlines from biplane images. In general, the calculated magnifications and orientations are accurate to within approximately 1-3% and 2-5 degrees, respectively. Here, we present a complete system for determination of the 3D vessel centerlines from biplane angiograms without the use of a calibration object. Subsequent to indication of the vessel centerlines, the imaging geometry and 3D centerlines are calculated automatically and within approximately 2 min. The system was evaluated in terms of the intra- and inter-user variations of the various calculated quantities. The reproducibilities obtained with this system are comparable to or better than the accuracies and reproducibilities quoted for other proposed methods. Based on these results and those reported in earlier studies, we believe that this system will provide accurate and reproducible vascular tree centerlines from biplane images while the patient is still on the table, and thereby will facilitate interventions and associated quantitative analyses of the vasculature.

Coronary Angiography↗
PubMed2000

Electroporation-enhanced gene delivery in mammary tumors.

Electroporation was applied to enhance gene transfer into subcutaneous MC2 murine breast tumors. Cultured MC2 cells were also transfected by electroporation or by cationic liposomes in the presence of serum using pSV-luc plasmids. Electroporation parameters and liposome formulation were optimized to achieve the highest relative levels of transfection. An electric field threshold for successful electrotransfection in cultured cells appeared around 800-900 V/cm. The liposomes used contained the cationic lipid dioleoyl-3-trimethylammonium propane (DOTAP). Multilamellar vesicles (MLV) had a 10-fold advantage over small unilamellar vesicles (SUV) in cell culture transfection. For in vivo gene delivery, the plasmids were injected either alone, or in complex with MLV or SUV DOTAP liposomes. A series of six electric pulses 1 ms long were applied across tumors, using caliper electrodes on the skin surface. Electric field strengths ranged from 400-2300 V/cm. Luciferase expression was approximately two orders of magnitude higher than controls in tumors treated with pulses > or =800 V/cm. Differences between enhanced relative levels of transfection using uncomplexed plasmid and lipoplexes were not statistically significant. Distribution of DNA into tumor tissues was monitored by fluorescence in situ PCR. The highest numbers of fluorescent cells were found in tumors electroporated following the injection of plasmid. The significant transfection improvement shows that in vivo electroporation is a powerful tool for local gene delivery to tumors.

Animals↗
PubMed2000

Bayesian inference for kappa from single and multiple studies.

Cohen's kappa coefficient is a widely popular measure for chance-corrected nominal scale agreement between two raters. This article describes Bayesian analysis for kappa that can be routinely implemented using Markov chain Monte Carlo (MCMC) methodology. We consider the case of m > or = 2 independent samples of measured agreement, where in each sample a given subject is rated by two rating protocols on a binary scale. A major focus here is on testing the homogeneity of the kappa coefficient across the different samples. The existing frequentist tests for this case assume exchangeability of rating protocols, whereas our proposed Bayesian test does not make any such assumption. Extensive simulation is carried out to compare the performances of the Bayesian and the frequentist tests. The developed methodology is illustrated using data from a clinical trial in ophthalmology.

Bayes Theorem↗
PubMed1999

Apoptosis induced by DNA uptake limits transfection efficiency.

Electrotransfection is an effective method for transfecting lymphoid cells. However, the transfection efficiency of certain lymphoid cells is low. L1210 subclones and NFS-70 pro-B cells, which are highly refractory to various transfection methods, were used to identify the limiting factors. Cells were electrotransfected with plasmids coding for green fluorescence protein or luciferase. The luciferase expression of L1210 subclone 3-3 was found to increase 6-12 h after electroporation, but decreased significantly from 12 to 48 h. The lower level of luciferase activity at later time periods correlated with decreases in cell viability, which was shown to be due to apoptosis, as determined by propidium iodide/acrindine orange staining, DNA laddering, and prevention of cell death by addition of caspase inhibitors. Similar results were observed with NFS-70 pro-B cells and select L1210 subclones. In contrast, L1210 parental and L1210 subclone 7-15.6 cells undergo only low levels of apoptosis (< or = 5%). Apoptosis occurred only when DNA (plasmids or salmon sperm DNA) was present during electroporation, but was not dependent on the conformation of the DNA used or the expression of transgenes. Cells pulsed in the presence of dextran sulfate (MW 500,000) did not apoptose. Similar results were observed when L1210 subclone 3-3 was transfected using the cationic lipid 1, 2-dioleoyl-3-trimethylammonium propane, although the transfection efficiency and corresponding rate of apoptosis were significantly lower. Applying the caspase inhibitor fluoromethyl ketone (Boc-ASP-FMK) dramatically improved cell viability and transgene expression of select L1210 subclones and NFS-70 pro-B cells.

Amino Acid Chloromethyl Ketones↗
PubMed1999

Time-dependent ultrastructural changes to porcine stratum corneum following an electric pulse.

The morphological changes to heat-stripped porcine stratum corneum following an electroporating pulse were studied by time-resolved freeze fracture electron microscopy. Pulses at a supra-electroporation threshold of 80 volts and 300 microseconds were applied across the stratum corneum with a pair of copper plate electrodes, which also served as cooling contacts. Multilamellar vesicles of 0.1-5.5 mm in diameter in the intercellular lipid bilayers of the stratum corneum appeared in less than milliseconds after pulsing. Pulsed samples exhibited aggregations of vesicles, whereas only occasional single vesicles were seen in the unpulsed samples. Aggregates form in less than a millisecond and disappear within minutes after the pulse. Their size ranged from 0.3 to 700 mm2. The size of individual vesicles, aggregate density, and size were analyzed as functions of postpulse time. These aggregate formations seem to be a secondary reaction to the pulse-induced skin permeabilization, determined by the resistance drop and recovery after the pulse. Heating the samples to 65 degrees C also caused vesicle aggregates of similar appearance to form, suggesting that these aggregations are related to the heating effect of the pulse. Hydration is thought to play an important role in aggregate formation.

Administration, Cutaneous↗