Anthroponotic cutaneous leishmaniasis in Kabul, Afghanistan: the high susceptibility of Phlebotomus sergenti to Leishmania tropica.
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Afghanistan↗
Biomedical subjects
Y Tang
Publications and source records attributed to Y Tang.
Improved processing of the steady-state evoked potential.
Two related procedures for estimating the parameters of steady-state evoked potentials (SSEPs) are introduced. The first procedure involves an initial stage of digital bandpass filtering followed by a Discrete Fourier Transform analysis. In the second method, a high resolution method based on parametric modelling is applied to the filtered data. The digital pre-filter consists of a non-phase shifting Chebychev bandpass filter. The parametric modelling method considers the evoked-response-plus-noise distribution to consist of a set of exponentially damped sinusoids. The frequency, amplitude, phase and damping factors of these components are estimated by calculating the mean of the forward and backward prediction filters and linear regression. We compared the signal-to-noise ratio (SNR) of the new procedures to the conventional Discrete Fourier Transform method for Monte Carlo simulations utilizing known sinusoids buried in white noise, known sinusoids buried in human EEG noise and for a sample of visual evoked potential data. Both of the new methods produce substantially more accurate and less variable estimates of test sinusoid amplitude. For VEP recording, the EEG background noise level is reduced by 5-6 dB over that obtained with the DFT. The new methods also provide approximately 5 dB better SNR than the DFT for detection of sinusoids based on the Rayleigh statistic. The parametric modelling approach is particularly suited for the analysis of very short data records including cycle-by-cycle analysis of the SSEP.
Brain↗
Age-induced white matter changes in the human brain: a stereological investigation.
In the present pilot study, age-related white matter changes were investigated by the use of design-based stereological methods. In the brains of elderly subjects, the total volume of the white matter and the total volume of the myelinated fibers therein were lower than in those of young subjects (15% and 17%, respectively), but the differences were not statistically significant. The total length of the myelinated fibers of the white matter in the elderly group of 86,000 km was, statistically, significantly decreased by 27% compared with 118,000 km in the young group. This loss of the total nerve fiber length was accompanied in particular by a decline of the myelinated fibers with a small diameter. The mean diameter of the myelinated fibers in the young group was significantly smaller than in the old group, but the relative size distributions of the myelinated fiber diameters between the young and old groups were similar. Our findings show that the atrophy of the human white matter during ageing is probably caused by a loss of myelinated fibers with a small diameter.
Adult↗
Congenital anomalies of the pancreaticobiliary tract: findings on MR cholangiopancreatography (MRCP) using half-Fourier-acquisition single-shot turbo spin-echo sequence (HASTE).
The clinical significance of magnetic resonance cholangiopancreatography (MRCP) using half-Fourier acquisition single-shot turbo spin-echo (HASTE) in the evaluation of congenital anomalies of pancreaticobiliary tract was demonstrated in 56 patients (man: 31, women: 25; age: 0-60 years old, mean 15 years old) with suspected congenital anomalies of pancreaticobiliary tract. The image quality and characteristics were assessed. MRCP using HASTE with a phased array coil can be used as a non-invasive method for the evaluation of congenital anomalies of the pancreaticobiliary tracts.
Adolescent↗
Experimental study on HASTE sequences: impacts of parameters on liver imaging.
This study investigates the impacts of effective TE (TEeff), echo spacing and echo train lengths (ETLs) on the imaging quality of HASTE sequences for liver imaging through a slit and a liver phantom. The HASTE sequence with a short echo spacing demonstrated higher CNR for a phantom simulating hepatocellular carcinoma (HCC) than that with long echo spacing. With a long echo spacing, the HASTE sequence showed higher spatial resolution for hemangiomas and metastasis. The improvement of spatial resolution along with the increase in ETLs (imaging matrix) was more prominent for hemangioma than for HCC.
Carcinoma, Hepatocellular↗
Spin-echo echo-planar MR imaging of hepatocellular carcinoma arising from chronic liver damage: comparison with turbo spin-echo imaging.
The aim of this work was to evaluate the value of echo-planar imaging (EPI) in the detection of hepatocellular carcinomas arising in a chronic liver damage to respiratory triggered turbo spin-echo (TSE) imaging. With spin-echo EPI sequences, better lesion-liver contrast was obtained than TSE imaging. Although severe artifact is seen, this imaging produce good contrast, and may be useful as an adjunct to TSE imaging in evaluating patients with chronic liver damage.
Adolescent↗
Ultrafast fetal MR images of sacrococcygeal teratoma: a case report.
A case of sacrococcygeal teratoma diagnosed at 31 weeks' gestation by fetal MR imaging is presented. For fetal MR imaging, an ultrafast imaging sequence, Half-Fourier acquisition single shot turbo spin echo (HASTE) was employed. The HASTE sequence enabled us to obtain high resolution images in a short time and was particularly useful in enabling better contrast between the cystic and solid components of the tumor.
Female↗
Synthesis of novel folic acid-functionalized biocompatible block copolymers by atom transfer radical polymerization for gene delivery and encapsulation of hydrophobic drugs.
Two synthetic routes to folic acid (FA)-functionalized diblock copolymers based on 2-(methacryloyloxy)ethyl phosphorylcholine [MPC] and either 2-(dimethylamino)ethyl methacrylate [DMA] or 2-(diisopropylamino)ethyl methacrylate [DPA] were explored. The most successful route involved atom transfer radical polymerization (ATRP) of MPC followed by the tertiary amine methacrylate using a 9-fluorenylmethyl chloroformate (Fmoc)-protected ATRP initiator. Deprotection of the Fmoc groups produced terminal primary amine groups, which were conjugated with FA to produce two series of novel FA-functionalized biocompatible block copolymers. Nonfunctionalized MPC-DMA diblock copolymers have been previously shown to be effective synthetic vectors for DNA condensation; thus, these FA-functionalized MPC-DMA diblock copolymers appear to be well suited to gene therapy applications based on cell targeting strategies. In contrast, the FA-MPC-DPA copolymers are currently being evaluated as pH-responsive micellar vehicles for the delivery of highly hydrophobic anticancer drugs.
Biocompatible Materials↗
Evaluation of immunoglobulins from plant cells.
Expression of cDNA constructs encoding full-length mouse immunoglobulin chains with their native leader sequences or fusion constructs substituting the native leader with a pre-pro sequence derived from Saccharomyces cerevisiae yielded blocked N-termini on the gamma chain or the correct amino terminal sequence on the mature kappa chain. Lectin binding assays revealed that assembled immunoglobulin complexes contained a glycosylated heavy chain. The attached glycan was resistant to digestion by endoglycosidase H and its lectin binding pattern was distinguishable from that of the mammalian glycan. The results indicated processing of the immunoglobulin carbohydrate in the tobacco Golgi to yield a complex oligosaccharide. Secretion of antibody by protoplasts isolated from regenerated transgenic plants or from suspension callus cells was demonstrated by pulse-chase labeling experiments. When purified, the tobacco-produced antibody was found to possess the antigen binding and catalytic properties of the murine monoclonal antibody. Kinetic parameters (Km, Ki, Vmax, and kcat) of the tobacco-derived antibody were comparable to those of the mouse-derived antibody. The results in general show that the endomembrane system of tobacco cells possesses cognate mechanisms for the recognition of diverse leader sequences. These signals can be used to initiate the assembly, processing, and secretion by plant cells of complex foreign proteins.
Amino Acid Sequence↗
Structural features of toxic chemicals for specific toxicity.
We have studied the structural features of toxic chemicals from the RTECS database associated with specific toxicity. The frameworks, functional groups, and structure patterns of molecules are taken into account. Potential active frameworks, groups, and structure patterns for specific toxicity are gained by computational chemistry approaches. These structural features of toxic chemicals will be helpful in understanding activities of toxic chemicals and useful in predicting the toxicity of chemicals, especially in the early stage of drug design.
Database Management Systems↗
Detection of spontaneous schwannomas by MRI in a transgenic murine model of neurofibromatosis type 2.
Spontaneous schwannomas were detected by magnetic resonance imaging (MRI) in a transgenic murine model of neurofibromatosis type 2 (NF2) expressing a dominant mutant form of merlin under the Schwann cell-specific P0 promoter. Approximately 85% of the investigated mice showed putative tumors by 24 months of age. Specifically, 21% of the mice showed tumors in the intercostal muscles, 14% in the limb muscles, 7% in the spinal cord and spinal ganglia, 7% in the external ear, 14% in the muscle of the abdominal region, and 7% in the intestine; 66% of the female mice had uterine tumors. Multiple tumors were detected by MRI in 21% of mice. The tumors were isointense with muscle by T1-weighted MRI, showed strong enhancement following administration of gadolinium-DTPA, and were markedly hyperintense by T2-weighted MRI, all hallmarks of the clinical manifestation. Hematoxylin and eosin staining and immunohistochemistry indicated that the tumors consisted of schwannomas and Schwann cell hyperplasias. The lesions stained positively for S-100 protein and a marker antigen for the mutated transgenic NF2 protein, confirming that the imaged tumors and areas of hyperplasia were of Schwann cell origin and expressed the mutated NF2 protein. Tumors were highly infectable with a recombinant herpes simplex virus type 1 vector, hrR3, which contains the reporter gene, lacZ. The ability to develop schwannoma growth with a noninvasive imaging technique will allow assessment of therapeutic interventions.
Animals↗
An algorithm to match registries with minimal disclosure of individual identities.
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Algorithms↗
Fast breath-hold T2-weighted MRI of the kidney by means of half-Fourier single-shot turbo spin echo: comparison with high resolution turbo spin echo sequence.
PURPOSE: The value of the fast half-Fourier single-shot turbo spin echo (HASTE) sequence in T2-weighted MRI of the kidney was evaluated as a substitute for the conventional turbo spin echo (TSE) sequence. METHOD: Forty-five patients with suspected abnormalities of the kidney underwent MRI with a 1.5 T system. Breath-hold HASTE and respiratory-triggered TSE sequences were performed. Qualitative and quantitative analyses were performed for comparison of these sequences. RESULTS: The signal-to-noise ratio (SNR) with HASTE was higher than that with TSE. The lesion-to-kidney contrast-to-noise ratio for solid masses with HASTE was almost equal to that with TSE. For cystic masses, the CNR with HASTE was significantly higher than that with TSE (p < 0.05). Respiratory and chemical shift artifacts were significantly smaller on HASTE than on TSE (p < 0.01). However, the blurring artifact was higher on HASTE than on TSE (p = 0.01). CONCLUSION: The HASTE sequence generates high contrast images and is free of motion and chemical shift artifacts, with much better time efficacy. The sequence provides comparable diagnostic information to TSE sequences.
Adult↗
Cloning of the human homolog of mouse transmembrane tryptase.
BACKGROUND: Three functionally distinct tryptases have been identified in the mouse, one of which encodes an unusual protease that possesses a membrane-spanning domain located in its C terminus. METHODS AND RESULTS: Using the deduced nucleotide sequence of this mouse transmembrane tryptase (mTMT) gene in a polymerase chain reaction approach, cDNAs were isolated from a number of tissues which encode its human homolog. The amino acid sequences of hTMT and mTMT are 74% identical, and the human tryptase also has the novel membrane-spanning domain. CONCLUSION: The discovery that the human genome contains a large number of homologous, but distinct, tryptase genes suggests that the individual members of this family of proteases evolved to carry out discrete functions in mast cell-mediated allergic reactions.
Amino Acid Sequence↗
Metastatic liver tumor from cystic ovarian carcinomas: CT and MRI appearance.
OBJECTIVE: The initial and follow-up CT and MRI images of ten patients with hepatic metastases from ovarian tumors were retrospectively analyzed to establish their features and sequential changes in appearance. MATERIALS AND METHODS: Ten patients with hepatic metastasis from ovarian tumors received initial and follow-up CT and MRI examinations. Six patients were followed up every two to three weeks before surgical tumor resection. Both CT and MR images were analyzed by two radiologists. RESULTS: A total of fourteen lesions were detected by CT and MRI in 10 patients. All 14 lesions were demonstrated as areas of marked hyperintensity on T2-weighted MRI. Eleven cyst-like tumors were demonstrated as round or oval low density lesions on CT and as areas of hypointensity on T1-weighted imaging. Three lesions were shown as solid masses with slightly low attenuation at the initial CT examination and slightly low or iso-intensity areas on T1-weighted imaging, and these lesions showed early peripheral globular enhancement and delayed enhancement on contrast-enhanced CT and MR imaging. Cystic formation was observed two to three weeks later after initial study in all the 3 solid lesions. Rapid subcapsular effusion, which showed obvious enhancement on delayed Gd-DTPA enhanced MR imaging, was observed in two patients. CONCLUSION: The hepatic metastatic tumor from cystic ovarian carcinoma may manifest as a well-defined cystic lesion or as a solid mass, and the solid mass shows delayed enhancement on contrast-enhanced CT and MR imaging. Furthermore, rapid cystic formation and rapid subcapsular extension is frequently seen.
Adult↗
Solid-phase extraction method for patulin in apple juice and unfiltered apple juice.
Patulin, a mold metabolite, is commonly found in rotting apples. Some countries regulate patulin at levels ranging from 30 to 50 micrograms/L. Most analytical methods for patulin in apple juice include liquid-liquid partitions. A solid-phase extraction method has been developed for apple juice and unfiltered apple juice in the United States. A portion of the test sample (5 mL) was passed through a macroporous copolymer cartridge and was washed with 1 mL 1% sodium bicarbonate and then with 1 mL 1% acetic acid. Patulin was eluted with 3 mL 2% acetonitrile in anhydrous ethyl ether and was determined by reversed-phase liquid chromatography with UV detection at 276 nm. Recoveries ranged from 93 to 104% in test samples spiked at 20-100 micrograms/L.
Chromatography, Liquid↗
Calculation of T2 relaxation time from ultrafast single shot sequences for differentiation of liver tumors: comparison of echo-planar, HASTE, and spin-echo sequences.
PURPOSE: The purpose of this study was to evaluate the accuracy of T2 calculation from single shot imaging sequences such as echo-planar imaging (EPI) and half-Fourier single shot turbo spin-echo (HASTE) imaging. MATERIALS AND METHODS: For the phantom study, we prepared vials containing different concentrations of agarose, copper sulfate, and nickel chloride. The temperature of the phantom was kept at 22 degrees C. MR images were obtained with a 1.5-Tesla superconductive magnet. Spin-echo (SE) -type EPI and HASTE sequences with different TEs were obtained for T2 calculation, and the T2 values were compared with those obtained from the Carr-Purcell-Meiborm-Gill (CPMG) sequence. The clinical study group consisted of 30 consecutive patients referred for MR imaging to characterize focal liver lesions. A total of 40 focal liver lesions were evaluated, including 25 primary or metastatic solid masses and 15 non-solid lesions. Single shot SE-type EPI and HASTE were both performed with TEs of 64 and 90 msec. RESULTS: In the phantom study, the T2 values obtained from both single shot sequences showed significant correlations with those from the CPMG sequence (T2 on EPI vs. T2 on CPMG: r=0.98, p<0.01; T2 on HASTE vs. T2 on CPMG: r=0.99, p<0.01). In the clinical study, mean T2 values for liver calculated from EPI (42 msec) were significantly shorter than those calculated from the HASTE sequence (58 msec) (p<0.001). Mean T2 values for solid tumors were 95 msec with HASTE and 72 msec with EPI, and mean T2 values for non-solid lesions were 128 msec with HASTE and 159 msec with EPI. Although mean T2 values between solid and non-solid lesions were significantly different for both EPI and HASTE sequences (p=0.01 for HASTE, p<0.001 for EPI), the overlap of solid and non-solid lesions was less frequent in EPI than in HASTE. CONCLUSION: With single shot sequences, it is possible to obtain the T2 values that show excellent correlation with the CPMG sequence. Although both HASTE and EPI are useful to calculate T2 values, EPI appears to be more accurate in characterizing focal liver lesions.
Adult↗
The value of fast and ultrafast T2-weighted MR imaging sequences in hepatic enhancement with ferumoxides: comparison with conventional spin-echo sequence.
PURPOSE: The efficacy of superparamagnetic iron oxide (SPIO) was evaluated with fast T2-weighted imaging sequences such as turbo spin-echo (TSE), half-Fourier single shot turbo spin echo (HASTE), and echo-planar imaging (EPI) in comparison with the conventional spin-echo (SE) sequence on a 1.5 Tesla MR unit. MATERIALS AND METHODS: In a phantom study, we prepared vials containing different concentrations of ferumoxides (0, 0.25, 0.5, 0.75, and 1 micromol Fe) in 2% agarose simulating the liver. In an animal study, contrast medium in doses of 10, 20, and 30 micromol/kg of ferumoxides was injected into the ear vein of rabbits weighing 3.0-4.0 kg under general anesthesia. MR imaging of the phantom and liver of the rabbits was obtained with the T2-weighted SE sequence (TR/TE=2000/20, 80), TSE sequences (TR/effective TE=2000/90, echo train length=7), HASTE (effective TE=64, 90 msec), and EPI (effective TE=64, 90 msec). Three rabbits in each group were imaged before and 1 hour after ferumoxides administration for in-vivo study. The Signal intensity of pre- and postcontrast imaging of the phantom or rabbits' livers was measured with operator-defined regions of interest, and signal-to-noise ratios (SNR) were obtained. Immediately after imaging, the rabbits were sacrificed and the livers were removed at autopsy, followed by ex-vivo study. In a clinical study, 10 micromol/kg of ferumoxides was given in 34 consecutive patients with 31 solid tumors. The liver SNR were evaluated for all 34 patients, and tumor to-liver contrast-to-noise ratios (CNR) were evaluated for all 31 solid lesions. The same series of imaging techniques as in the experimental studies was performed for quantitative and qualitative analyses. RESULTS: In both in-vitro and in-vivo studies, SNR of the phantom or rabbits' livers significantly decreased after ferumoxides administration. The decrease in SNR on excised rabbits' livers was 72% for EPI, 36% for HASTE, 61% for SE, and 51% for TSE at a dose of 10 micromol/kg of ferumoxides. In the clinical study, HASTE and TSE showed significant improvement in CNRs after ferumoxides administration (p<0.05). Visual analysis revealed improvement in tumor detection for all sequences. On EPI, although contrast was excellent, severe image distortion was seen. Although the signal decrease with HASTE and TSE was somewhat inferior to those with EPI and SE, respectively, the effect of contrast enhancement on HASTE and TSE was marked on visual analysis. CONCLUSION: Although TSE sequences and HASTE sequences are less susceptible to magnetic field inhomogeneities than SE and EPI sequences, the decrease in liver signal on HASTE and TSE sequences was comparable to that on EPI and SE sequences, respectively. These sequences are useful clinically for ferumoxides imaging, because they are less sensitive to motion artifacts.
Adult↗