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Biomedical subjects

K Sen

Publications and source records attributed to K Sen.

At least 19 recordsLinked to original sources
PubMed2004

IgA monoclonal gammopathy of undetermined significance with peripheral neuropathy.

Monoclonal gammopathy of undetermined significance (MGUS) and peripheral neuropathy may be causally linked. In most cases, the M-protein is of IgG or IgM type. Peripheral neuropathy associated with IgA MGUS is uncommon, and there are limited reports. Here, we report a case of a 55-year-old male who was diagnosed to have symmetrical sensorimotor peripheral neuropathy associated with IgA MGUS with deposits of IgA-monoclonal protein in the myelin sheath.

Humans↗
PubMed2004

Distribution of six virulence factors in Aeromonas species isolated from US drinking water utilities: a PCR identification.

AIMS: To examine whether Aeromonas bacteria isolated from municipally treated water had virulence factor genes. METHODS AND RESULTS: A polymerase chain reaction-based genetic characterization determined the presence of six virulence factors genes, elastase (ahyB), lipase (pla/lip/lipH3/alp-1) flagella A and B (flaA and flaB), the enterotoxins, act, alt and ast, in these isolates. New primer sets were designed for all the target genes, except for act. The genes were present in 88% (ahyB), 88% (lip), 59% (fla), 43% (alt), 70% (act) and 30% (ast) of the strains, respectively. Of the 205 isolates tested only one isolate had all the virulence genes. There was a variety of combinations of virulence factors within different strains of the same species. However, a dominant strain having the same set of virulence factors, was usually isolated from any given tap in different rounds of sampling from a single tap. CONCLUSIONS: These results show that Aeromonas bacteria found in drinking water possess a wide variety of virulence-related genes and suggest the importance of examining as many isolates as possible in order to better understand the health risk these bacteria may present. SIGNIFICANCE AND IMPACT OF THE STUDY: This study presents a rapid method for characterizing the virulence factors of Aeromonas bacteria and suggests that municipally treated drinking water is a source of potentially pathogenic Aeromonas bacteria.

Aeromonas↗
PubMed2001

Multiplex PCR for detection of Enterobacteriaceae in blood.

BACKGROUND: Rapid and sensitive methods are needed to detect the small numbers of bacteria that may sometimes contaminate units of blood during collection. A multiplex 5'-nuclease TaqMan PCR assay (PE Applied Biosystems) was used to detect several bacterial species that may contaminate blood. STUDY DESIGN AND METHODS: Oligonucleotide primers were made for regions of the 16S rRNA gene conserved in four different bacterial species: Yersinia enterocolitica and Serratia, Klebsiella, and Enterobacter species. Two probes were designed: SL-1 detected Serratia, Klebsiella, and Enterobacter species, and YE-3 detected Y. enterocolitica. RESULTS: When TaqMan PCR was performed with chromosomal DNA isolated from pure cultures of Serratia liquefaciens, Klebsiella oxytoca, Klebsiella pneumoniae, Enterobacter cloacae, and Enterobacter agglomerans, the limit of detection with probe SL-1 was 1 to 2 CFUs. For S. marcescens, the sensitivity was 8 CFUs. The limit of detection for Y. enterocolitica with probe YE-3 was 2 CFUs. When total chromosomal DNA was extracted from whole-blood samples spiked with different numbers of Y. enterocolitica, S. liquefaciens, E. cloacae, or K. pneumoniae bacteria, the TaqMan PCR detected 12 to 16 organisms in 1 mL of blood. CONCLUSION: The 5'-nuclease TaqMan PCR assay takes only 3 hours to perform and has the potential to detect very small numbers of bacteria.

Blood↗
PubMed2001

Feature analysis of natural sounds in the songbird auditory forebrain.

Although understanding the processing of natural sounds is an important goal in auditory neuroscience, relatively little is known about the neural coding of these sounds. Recently we demonstrated that the spectral temporal receptive field (STRF), a description of the stimulus-response function of auditory neurons, could be derived from responses to arbitrary ensembles of complex sounds including vocalizations. In this study, we use this method to investigate the auditory processing of natural sounds in the birdsong system. We obtain neural responses from several regions of the songbird auditory forebrain to a large ensemble of bird songs and use these data to calculate the STRFs, which are the best linear model of the spectral-temporal features of sound to which auditory neurons respond. We find that these neurons respond to a wide variety of features in songs ranging from simple tonal components to more complex spectral-temporal structures such as frequency sweeps and multi-peaked frequency stacks. We quantify spectral and temporal characteristics of these features by extracting several parameters from the STRFs. Moreover, we assess the linearity versus nonlinearity of encoding by quantifying the quality of the predictions of the neural responses to songs obtained using the STRFs. Our results reveal successively complex functional stages of song analysis by neurons in the auditory forebrain. When we map the properties of auditory forebrain neurons, as characterized by the STRF parameters, onto conventional anatomical subdivisions of the auditory forebrain, we find that although some properties are shared across different subregions, the distribution of several parameters is suggestive of hierarchical processing.

Animals↗
PubMed2001

Competitive amino acid transport between L-tryptophan and other amino acids in Schizophyllum commune.

In our study on nutritional requirement for the hyphal growth of Schizophyllum commune, we found that a Trp- mutant could not grow in the L-Trp-supplied medium in the presence of L-Ser. Further growth studies showed that not only L-Ser but also as many as 11 kinds of amino acid including L-Ala, L-Arg, L-Asn, L-His, L-Leu, L-Met, L-Phe, L-Ser, L-Thr, L-Tyr and L-Val inhibited the growth of the Trp- mutant in the L-Trp-supplied medium. However, these amino acids did not inhibit the growth of a Trp+ strain. The inhibition of growth of Trp+ strain induced by a Trp analogue of 5-fluoro-DL-tryptophan (5FT), which was usually recovered by L-Trp, was rescued by the same amino acids mentioned above. The exceptions were Gly and L-Ile, which also recovered the growth inhibition induced by 5FT. These results indicate that the permease responsible for the Trp transport in S. commune might also be active to other amino acids. However, it is considered that the permease shows high affinity to L-Trp and low affinity to other amino acids. As a result, the transport of L-Trp and 5FT may be counteracted by other amino acids.

Journal Article↗
PubMed2000

Cloning and sequencing analysis of Trp1 gene of Flammulina velutipes.

The genomic TRP1 gene from basidiomycete Flammulina velutipes was cloned by complementation of yeast Saccharomyces cerevisiae trp1 mutation. Sequencing analysis revealed that the TRP1 gene encoded a single protein consisting of three catalytic functional domains; glutamine amidotransferase, indole-3-glycerol phosphate synthase ) and N-(5'-phosphoribosyl) anthranilate isomerase, in order of NH2-glutamine amidotransferase-indole-3-glycerol phosphate synthase N-(5'-phosphoribosyl) anthranilate isomerase-COOH. The coding sequence of the TRP1 gene was interrupted by a single intron of 48 bases, the position and flanking sequences of which were highly homologous to those of basidiomycete Phanerochaete chrysosporium trpC.

Agaricales↗
PubMed2000

Basidiomycetous fungus Flammulina velutipes harbors two linear mitochondrial plasmids encoding DNA and RNA polymerases.

Basidiomycetous fungus Flammulina velutipes R15 strain had two linear plasmids in its mitochondria designated pFV1 and pFV2. They were double-stranded DNAs, whose sizes were 8.3 and 8.9 kb, respectively. Sequencing analysis of 7364 bases of the pFV1 and 6861 bases of the pFV2 revealed that the both plasmids had one set of two open reading frames (ORFs) each of that encoded putative DNA and RNA polymerases similar to those of mitochondrial plasmids in other filamentous fungi. In phylogenetic analysis of deduced amino acid sequences of the ORFs and counterparts of other filamentous fungi, the pFV2 was expectedly clustered with plasmids of basidiomycetous fungi. whereas the pFV1 with kalilo plasmid of ascomycetous fungus Neurospora intermedia.

Agaricales↗
PubMed2000

Global health status: two steps forward, one step back.

Impressive improvements have occurred in global health status in the past century. Unfortunately, these improvements have not been shared equally and health in equalities within and among countries are entrenched. The fragility of health gains has been seen in response to economic, political, and social changes changes, and civil disruption. The limitations of health-status measure hinder our ability to map health trends except in the simplest way. There is an urgent need for better regional and national health surveillance systems to underpin efforts to address the complex mixture of old and new health concerns.

Adolescent↗
PubMed2000

Spectral-temporal receptive fields of nonlinear auditory neurons obtained using natural sounds.

The stimulus-response function of many visual and auditory neurons has been described by a spatial-temporal receptive field (STRF), a linear model that for mathematical reasons has until recently been estimated with the reverse correlation method, using simple stimulus ensembles such as white noise. Such stimuli, however, often do not effectively activate high-level sensory neurons, which may be optimized to analyze natural sounds and images. We show that it is possible to overcome the simple-stimulus limitation and then use this approach to calculate the STRFs of avian auditory forebrain neurons from an ensemble of birdsongs. We find that in many cases the STRFs derived using natural sounds are strikingly different from the STRFs that we obtained using an ensemble of random tone pips. When we compare these two models by assessing their predictions of neural response to the actual data, we find that the STRFs obtained from natural sounds are superior. Our results show that the STRF model is an incomplete description of response properties of nonlinear auditory neurons, but that linear receptive fields are still useful models for understanding higher level sensory processing, as long as the STRFs are estimated from the responses to relevant complex stimuli.

Acoustic Stimulation↗
PubMed2000

A feasibility study of chemosensitivity assay by adhesive tumor cell culture system using biopsy specimens for gastric cancer.

BACKGROUND AND OBJECTIVES: The adhesive tumor cell culture system (ATCCS) is known to produce high colony-forming efficiency. We, therefore, studied the feasibility of ATCCS for gastric cancer by use of biopsy specimens and the relationship between the results of ATCCS and histological effects of anticancer drugs. METHODS: Tumor specimens extracted by gastroendoscopic biopsy were sufficient for obtaining the result of sensitivity to at least one drug in 24 out of 30 (80%) patients. Twenty patients were administered 5-fluorouracil (5-FU) for 14 days prior to surgery, and the results of ATCCS were compared with histological changes of the resected specimens. RESULTS: The histological response rate was found to be 100% (4/4) when the 90% inhibition concentration (IC90) of 5-FU was less than 0.24 microg/ml (sensitive) and was 0% (0/3) when IC90 was greater than 0.40 microg/ml (resistant). CONCLUSIONS: Although lacking in statistical significance, the results suggest that the drug to which the tumor revealed sensitivity in the ATCCS would produce histological effects and the drug to which the tumor was resistant would have no histological effect.

Aged↗
PubMed2000

Characterization of the relA gene of Porphyromonas gingivalis.

Based upon the nucleotide sequence of the relA gene from Escherichia coli, a gene fragment corresponding to the homologous gene from the pathogenic oral bacterium Porphyromonas gingivalis 381 was isolated by PCR and utilized to construct a relA mutant. The mutant, KS7, was defective in ribosome-mediated ppGpp formation and also in the stringent response.

Amino Acid Sequence↗
PubMed2000

Rapid identification of Yersinia enterocolitica in blood by the 5' nuclease PCR assay.

Yersinia enterocolitica accounts for 50% of the clinical sepsis episodes caused by the transfusion of contaminated red blood cells. A 5' nuclease TaqMan PCR assay was developed to detect Y. enterocolitica in blood. Primers and a probe based on the nucleotide sequence of the 16S rRNA gene from Y. enterocolitica were designed. Whole-blood samples were spiked with various numbers of Y. enterocolitica cells, and total chromosomal DNA was extracted. When the TaqMan PCR assay was performed, as few as six bacteria spiked in 200 microliter of blood could be detected. The assay was specific and did not detect other Yersinia species. The TaqMan assay is easy to perform, takes 2 h, and has the potential for use in the rapid detection of Y. enterocolitica contamination in stored blood units.

DNA, Ribosomal↗
PubMed1998

"True" mycotic aneurysm of a renal artery allograft.

A 60-year-old white man sustained a rupture of the renal artery 6 weeks after a cadaveric kidney transplantation. The bleeding site was repaired, and culture of the hematoma showed an isolated growth of Candida albicans. Blood and urine cultures were negative. Systemic antifungal therapy was initiated. Bleeding from the renal artery recurred, eventually requiring removal of the transplanted kidney. Histopathology of the resected specimen showed budding yeast in the wall of the renal artery, but no evidence of fungal invasion of the kidney. The patient received 6 weeks of amphotericin B therapy and currently remains on hemodialysis therapy.

Aneurysm, Infected↗
PubMed1998

Temporal dynamics of convergent modulation at a crustacean neuromuscular junction.

At least 10 different substances modulate the amplitude of nerve-evoked contractions of the gastric mill 4 (gm4) muscle of the crab, Cancer borealis. Serotonin, dopamine, octopamine, proctolin, red pigment concentrating hormone, crustacean cardioactive peptide, TNRNFLRFamide, and SDRNFLRFamide increased and -allatostatin-3 and histamine decreased the amplitude of nerve-evoked contractions. Modulator efficacy was frequency dependent; TNRNFLRFamide, proctolin, and allatostatin-3 were more effective when the motor neuron was stimulated at 10 Hz than at 40 Hz, whereas the reverse was true for dopamine and serotonin. The modulators that were most effective at high stimulus frequencies produced a significant decrease in muscle relaxation time; those that were most effective at low stimulus frequencies produced modest increases in relaxation time. Thus modulator actions that appear redundant when examined only at one stimulus frequency are differentiated when a range of stimulus dynamics is studied. The effects of TNRNFLRFamide, serotonin, proctolin, dopamine, and -allatostatin-3 on the amplitude and facilitation of nerve-evoked excitatory junctional potentials (EJPs) in the gm4 and gastric mill 6 (gm6) muscles were compared. The EJPs in gm4 have a large initial amplitude and show relatively little facilitation, whereas the EJPs in gm6 have a small initial amplitude and show considerable facilitation. Modulators that enhanced contractions also enhanced EJP amplitude; -allatostatin-3 reduced EJP amplitude. The effects of these modulators on EJP amplitude were modest and showed no significant frequency dependence. This suggests that the frequency dependence of modulator action on contraction results from effects on excitation-contraction coupling. The modulators affected facilitation at these junctions in a manner consistent with a change in release probability. They produced a change in facilitation that is inversely related to their action on EJP amplitude.

Animals↗
PubMed1997

A quantitative description of short-term plasticity at excitatory synapses in layer 2/3 of rat primary visual cortex.

Cortical synapses exhibit several forms of short-term plasticity, but the contribution of this plasticity to visual response dynamics is unknown. In part, this is because the simple patterns of stimulation used to probe plasticity in vitro do not correspond to patterns of activity that occur in vivo. We have developed a method of quantitatively characterizing short-term plasticity at cortical synapses that permits prediction of responses to arbitrary patterns of stimulation. Synaptic responses were recorded intracellularly as EPSCs and extracellularly as local field potentials in layer 2/3 of rat primary visual cortical slices during stimulation of layer 4 with trains of electrical stimuli containing random mixtures of frequencies. Responses exhibited complex dynamics that were well described by a simple three-component model consisting of facilitation and two forms of depression, a stronger form that decayed exponentially with a time constant of several hundred milliseconds and a weaker, but more persistent, form that decayed with a time constant of several seconds. Parameters obtained from fits to one train were used to predict accurately responses to other random and constant frequency trains. Control experiments revealed that depression was not caused by a decrease in the effectiveness of extracellular stimulation or by a buildup of inhibition. Pharmacological manipulations of transmitter release and postsynaptic sensitivity suggested that both forms of depression are mediated presynaptically. These results indicate that firing evoked by visual stimuli is likely to cause significant depression at cortical synapses. Hence synaptic depression may be an important determinant of the temporal features of visual cortical responses.

Animals↗
PubMed1997

Identification of a second transcriptional start site for the insecticidal protein gene cryIVA of Bacillus thuringiensis subsp. israelensis.

Expression of cryIVA, one of the insecticidal protein genes of B. thuringiensis subsp. israelensis, is regulated at the transcriptional level. The cryIVA gene is specifically transcribed during the stationary phase of this bacterium. As shown in our previous report [Yoshisue et al. (1993a)], the transcription from the -364 position of the cryIVA gene is conducted by the major promoter P1 that is functional during middle stages of the stationary phase of B. thuringiensis. In the present study, we have identified a second transcriptional start point P2 for the cryIVA gene in addition to P1, the major transcriptional start point. The transcription from P2 of the cryIVA gene occurred later than that from P1, during later stages of stationary phase of B. thuringiensis subsp. israelensis. The -10 and -35 nt sequences upstream from P2 of cryIVA are similar to those of the omega 28-specific promoters of B. thuringiensis genes and of the omega K-specific promoters of B. subtilis genes. It is most likely that the region upstream from P2 of cryIVA contains the nt sequences that determine the omega 28-specific promoter, the second one, for the cryIVA gene.

Amino Acid Sequence↗