Search PubMed⌕ Search

Biomedical subjects

W Xu

Publications and source records attributed to W Xu.

At least 523 records · Page 29Linked to original sources
PubMed1993

Diffraction correction methods for insertion ultrasound attenuation estimation.

We describe diffraction effects in acoustic ultrasound attenuation coefficient estimation using an insertion technique. We characterize the estimation error produced by diffraction as a function of distance and nominal attenuation values. Two new methods for correcting for the diffraction effect are presented. They are termed the Theoretical Diffraction Correction (TDC) and Experimental Diffraction Correction (EDC) techniques, respectively. Experimental validation of the two techniques is also presented, using two different sets of ultrasound measurements obtained with 1 MHz and 500 kHz transducer pairs, respectively. Significant improvement in the accuracy of the acoustic attenuation coefficient is demonstrated using both techniques.

Computer Simulation↗
PubMed1993

Transmission electron microscopy, scanning tunneling microscopy, and atomic force microscopy of the cell envelope layers of the archaeobacterium Methanospirillum hungatei GP1.

Methanospirillum hungatei GP1 possesses paracrystalline cell envelope components including end plugs and a sheath formed from stacked hoops. Both negative-stain transmission electron microscopy (TEM) and scanning tunneling microscopy (STM) distinguished the 2.8-nm repeat on the outer surface of the sheath, while negative-stain TEM alone demonstrated this repeat around the outer circumference of individual hoops. Thin sections revealed a wave-like outer sheath surface, while STM showed the presence of deep grooves that precisely defined the hoop-to-hoop boundaries at the waveform nodes. Atomic force microscopy of sheath tubes containing entrapped end plugs emphasized the end plug structure, suggesting that the sheath was malleable enough to collapse over the end plugs and deform to mimic the shape of the underlying structure. High-resolution atomic force microscopy has revised the former idea of end plug structure so that we believe each plug consists of at least four discs, each of which is approximately 3.5 nm thick. PT shadow TEM and STM both demonstrated the 14-nm hexagonal, particulate surface of an end plug, and STM showed the constituent particles to be lobed structures with numerous smaller projections, presumably corresponding to the molecular folding of the particle.

Cell Membrane↗
PubMed1993

Diagnosis of cytomegalovirus infections using polymerase chain reaction, virus isolation and serology.

The nested Polymerase Chain Reaction (PCR) was compared with virus isolation and serology to establish which is the best method for the diagnosis of active cytomegalovirus, (CMV) infection. Samples of blood leucocytes, urine and throat washings from immunosuppressed patients and patients with congenitally acquired CMV infection, as well as from healthy persons, were examined with PCR. CMV DNA was detected in all samples from which CMV could be isolated, but not from any sample from healthy adults, whether CMV seropositive or CMV seronegative. In contrast to the findings in healthy persons, CMV genomes were frequently detected in urine and throat washings from immunosuppressed, CMV-seropositive patients without symptoms of CMV infection. The appearance of CMV genomes in blood cells in immunosuppressed CMV-seronegative patients may be the first sign of primary CMV infection. Congenital CMV infection could be rapidly and safely diagnosed when urine samples were examined by PCR. Nested PCR is a valuable tool for the diagnosis of active CMV infection, when selected materials are used.

Adolescent↗
PubMed1993

[Influence of lesion of motor cortex on second somatosensory area emanating descending modulation on thalamic intralaminar nuclei].

The present study was undertaken to verify further the participation of motor cortex (MCtx) in the somatosensory area II(SII) emanating descending modulation of thalamic intralaminar nuclei (ILN). Neuronal responses in ILN to noxious stimulation of the superficial peroneal nerve were extracellularly recorded in 34 cats. The effects of electrical stimulating SII on nociceptive responses of neurons in ILN before and after lesion of MCtx were observed and compared. It was shown that electrical stimulation of SII obviously inhibited the nociceptive responses in the majority of neurons recorded (11/13) in ILN in the cats with MCtx intact (P < 0.05). After lesion of MCtx the inhibitory effect still remained (n = 10, P < 0.05), but weakened to a certain extent compared with that before lesion. In the animals with the lesion involving MCtx and the underlying subcortical structures electrical stimulating SII facilitated the nociceptive responses of ILN neurons (n = 7, P < 0.05). The results further support the idea that SII emanating descending modulation on ILN is in part fulfilled via MCtx.

Animals↗
PubMed1993

[Effects of stimulation of SmI and electroacupuncture on nociceptive responses of the ventrobasal complex].

In order to confirm the idea that the cerebral cortex is involved in acupuncture analgesia through descending modulation, the effects of stimulation of SmI and electroacupuncture on nociceptive responses of VB neurons were investigated. The experiments were carried out on lightly anesthetized rats. Single unit activities of VB neurons were extracellularly recorded with glass microelectrodes. The results showed that both electrical stimulation of SmI (n = 11) and electroacupuncture at left. "Huantiao" (G30) point (n = 11) could inhibit the nociceptive responses of VB neurons and their effects were similar. These results suggested that SmI may play a role in acupuncture analgesia through corticofugal modulation on VB.

Animals↗
PubMed1993

[Effect of electroacupuncture on peripheral microcirculation in acute experimental arthritic rats].

This paper reports the effect of electroacupuncture (EA) on peripheral microcirculation in 12 acute experimental arthritic rats and 6 healthy rats. The results showed that after EA an obvious improvement in footback-microcirculation of acute experimental arthritic rats appeared, namely, the disturbance of microcirculation on the area of pathological changes was alleviated. The auricular microcirculation was strengthened as well. There were no obvious changes of peripheral microcirculation in healthy rats after EA. That indicates EA has therapeutic effects of promoting blood circulation and reducing extravasated blood, antiphlogosis and detumescence on the area of pathological changes in acute experimental arthritic rat.

Animals↗
PubMed1993

[The extensiveness and specificity of analgesia of electroacupuncture (EA) at different points on the nociceptive responses of neuron in spinal dorsal horn].

The experiments were performed in anaesthetized rats. The responses of convergent neurons in spinal dorsal horn to noxious stimuli (10mA, 2ms) given at the hindpaw receptive field were recorded extracellularly by glass microelectrodes. The effects of EA on the nociceptive response were observed. EA was applied on ipsilateral "Zusanli" or "Xiaguan" point with high and low intensity. EA (18V, 100Hz) applied on ipsilateral either "Zusanli" or "Xiaguan" could produce strong inhibition on nociceptive responses of convergent neurones (62.74 +/- 4.94% and 64.24 +/- 7.30%). EA (2V, 100Hz) of "Zusanli" also obviously inhibited the nociceptive responses (52.05 +/- 6.69%). But the same EA of "Xiaguan" lacked this inhibitory effect (9.50 +/- 7.67%). There was statistically significant difference between EA effects of "Zusanli" and "Xiaguan" (P < 0.001) when intensity of EA is lower. These results suggested that analgesia of high intensity EA is extensive, but that of low intensity EA is produced only when the point is in the same or nearby spinal segment with nociceptive field, showing the extensiveness and specificity of EA analgesia of different points.

Acupuncture Analgesia↗
PubMed1993

[Observation on the relation between propagated sensation along meridians and the therapeutic effect of acupuncture on myopia of youngsters].

Nine hundred and ninety two eyes suffering from various degrees of myopia in 536 youngsters were treated with acupuncture. A method of exciting propagated sensation along meridians (PSM) and making it travel toward the affected region was employed in treatment. Bilateral Hegu (LI4) and Taichong (LR3); and bilateral Waiguan (ST5) and Guangming (GB37) were punctured on alternate days. The results showed that after 1-3 periods of treatment, the vision of 868 eyes (87.5%) were improved in various extent. Among them, the vision completely recovered in 131 eyes (13.31%), and the diopter decreased-0.75 to -1.00 D.S. in 13 eyes after acupuncture treatment. The therapeutic effect of acupuncture seemed to be considerably satisfactory and stable in two years following up. The extent of distinctness of PSM raised markedly with the increase of times of acupuncture. There was a close relation between the extent of distinctness of PSM and effectiveness of acupuncture. The more striking the centripetal PSM, the better was therapeutic effect of acupuncture. The excellent effect was always achieved when PSM arrived at the affected eye. Since PSM arrived at a large number of eyes in the subjects in younger year and so the better therapeutic effect was also achieved.

Acupuncture Therapy↗
PubMed1993

[Observation on the phenomenon of propagated sensation along meridians in youngsters].

That the opinion on the relation between the propagated sensation along meridians (PSM) and the age of the subjects was divergent in the results reported by some authors. In the last 10 years, we have performed a systematic investigation on PSM on a group of 536 youngsters. The main characteristics of PSM in youngsters were just the same as that of adults. However, the incidence of PSM in youngsters, particularly the degree of distinctness of PSM, was by far higher than that of adults. The results were stable and could be repeated in the experiments performed in different years. It showed that there was surely a close relation between the degree of distinctness of PSM and the age of subjects. This fact can not be appropriately explained at present. However, it provides an important clue to clarify the factors which influence the appearance of PSM, and in turn to promote the improvement of the therapeutic effect of acupuncture and cilacriation of the mechanism underlying the formation of PSM.

Acupuncture Therapy↗
PubMed1993

[Bronchiolitis obliterans with organizing pneumonia--a case report].

A case of bronchiolitis obliterans with organizing pneumonia was reported. Since the clinical symptoms, chest X-ray and lung function testings are all non-specific, open lung biopsy was performed. Final diagnosis was based on characteristic pathologic manifestations. Treatment with corticosteroid was very effective.

Adult↗
PubMed1993

Soft X-ray microimages of immunogold-labelled tumor cell surface antigens.

After successfully introducing the colloidal immunogold labelling technique to soft X-ray contact microscopy (SXCM), SXCM replica microimages of immunogold labelled tumor cell HLA-A2 surface antigens have been acquired for the first time. A biological sample preparation method using immunocytochemical staining techniques suitable for SXCM has also been established.

Antibodies, Monoclonal↗
PubMed1992

Evidence that Mos protein may not act directly on cyclin.

Using affinity-purified antiserum we have examined cyclin B2 levels in Xenopus oocytes at various stages of oogenesis. We found that cyclin B2 is detected from stage 2 to stage 6 as two bands, one of which is phosphorylated, and that cyclin B2 mass increases about 28-fold between stage 2 and stage 6. To examine the effect of Mos protein on cyclin phosphorylation, we microinjected synthetic Xenopus c-mos (c-mosxe) RNA into stages 4, 5, and 6 Xenopus oocytes. In stage 6 oocytes, maturation was induced by c-mosxe RNA, and, as is the case with progesterone treatment, all cyclin B2 was shifted to the phosphorylated form. However, c-mosxe RNA injected into stage 4 or 5 oocytes did not induce maturation or cause a shift in the relative proportion of the two cyclin B2 bands. These data suggest that Mos does not act directly to phosphorylate cyclin B2, causing the band shift during maturation. Cyclin B2 synthesis increases about 2-fold during maturation, in concert with total protein synthesis. Data from experiments on cyclin B2 stability indicate that the half-life of cyclin B2 is about 85 hr in stage 6. This suggests that if Mos protein has a direct effect on cyclin stability, it does so only at a later stage in oocyte maturation, but not at the onset.

Animals↗
PubMed1992

Karyotypic evolution of a murine mammary adenocarcinoma in vitro and during progression from primary to metastatic growth in vivo.

We have previously described a murine mammary tumor cell line (SP1) that metastasizes when transplanted into the mammary gland, but not when injected into the subcutaneous site. We used cytogenetic markers to assess genetic heterogeneity, and to monitor the selection and evolution of karyotypically distinct cell types during primary tumor growth and in metastases. The SP1 tumor cells are hypotetraploid (mean chromosome number = 72), and have at least four karyotypically distinct cell types. We found no consistent pattern of selection of tumor cell types in primary tumors. However, metastases were derived from a cell type that was present in the corresponding primary tumor. In addition, novel, karyotypically distinct cell types also appeared in the metastatic nodules. Markers that appeared in metastases included two translocations, t(10;18) and t(1;19). By injecting a mixture of cells from a metastatic nodule with a non-metastatic clone into mice, we showed that the new cell types in metastases displayed a stable increased growth and metastatic potential when compared to the non-metastatic clone, or when compared to the initial cell type from which the metastases derived. These results indicate that metastases are derived from a distinct cell type in the primary tumor, but that additional chromosome and cell evolution occurs, resulting in new cell types that are selected in metastases.

Adenocarcinoma↗