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Biomedical subjects

W Chen

Publications and source records attributed to W Chen.

At least 1,135 records · Page 63Linked to original sources
PubMed1990

Spatially-localized NMR spectroscopy employing an inhomogeneous surface-spoiling magnetic field gradient. 1. Phase coherence spoiling theory and gradient coil design.

The use of a current-generated, inhomogeneous, surface-spoiling magnetic field gradient for enhancing magnetic resonance spatial localization, by rapidly inducing spin phase incoherence in surface lying regions of a sample is examined theoretically. A geometrically simple surface-spoiling magnetic field gradient coil design is presented and its gradient field characterized via computer simulations. Mathematical expressions describing the time dependence of net sample spin phase coherence under influence of the spoiling gradient are developed for application with homogeneous (B1) volume coils. The dependence of spoiling efficiency on the magnetogyric ratio of the nuclide under investigation and on the current driving the gradient field is described. Spoiling periods of ca 1-2 ms with driving currents of ca 0.5-1.0 A are predicted to be adequate for surface-spoiling experiments with rat, e.g., for noninvasive monitoring of liver. A companion article (W. Chen and J.J.H. Ackerman, NMR Biomed., 3, 158-165 (1990)) describes implementation of the surface-spoiling technique with multicompartment models (phantoms) and with rat in vivo.

Equipment Design↗
PubMed1990

Spatially-localized NMR spectroscopy employing an inhomogeneous surface-spoiling magnetic field gradient. 2. Surface coil experiments with multicompartment phantom and rat in vivo.

The use of inhomogeneous surface-spoiling magnetic field gradients for elimination of signal from surface lying regions of a sample was theoretically examined in the companion article (W. Chen and J.J.H. Ackerman, NMR Biomed. 3, 147-157 (1990)). Using the spoiling gradient coil design described therein, this article presents experimental verification of the feasibility of such an approach to enhanced spatial localization. Single coil mode 31P NMR surface coil interrogation of both a two compartment phantom and rat in vivo are shown to provide excellent suppression of surface lying regions with minimal degradation of signal from the deep lying region of interest. Both pulse-and-collect and spin echo sequences were highly efficient in concert with spoiling gradient periods of 0.5-2 ms and driving currents of 0.5-2 A. The use of a current-generated surface spoiling gradient offers a robust means to remove surface tissue signal contributions and can be implemented with a wide range of localizing pulse sequences and imaging protocols.

Animals↗
PubMed1990

Inhibition in fat-storing cell multiplication by a factor produced by normal cultured murine hepatocytes.

In this study we demonstrate that hepatocytes isolated from normal mice may efficiently inhibit the multiplication of fat-storing cells (FSC) in culture, either in a coculture system where both cell types are separated by a filter of 0.45 microns pore size or via their conditioned medium. The inhibition may be completely reversed when the hepatocytes are removed and the culture medium is renewed. The inhibitory factor appears as early as 8 h in the medium with an almost maximum effect being reached after 24 h, as long as protein synthesis is allowed. It rapidly loses its efficiency through dilution. The inhibitory capacity of the conditioned medium is maintained after heating at 56 degrees C, dialysis of 100,000 x g centrifugation, but reduced after trypsin treatment. The infection of the hepatocytes by ectromelia virus causes an almost total suppression of the synthesis of the inhibitory factor. This latter result suggests that the multiplication of FSC, which may be inhibited by normal hepatocytes, would no longer be hindered in case of disregulation.

Animals↗
PubMed1990

Airway hypersensitivity induced by Ascaris suum extract in New Zealand Romney sheep.

Sheep from local farms with and without previous exposure to pigs were tested for their skin and airway responses to a commercial Ascaris suum antigen. There was an immediate reaction to intradermal injection of the antigen in 90% of 101 sheep. A bronchial provocation test by aerosol of the same antigen was undertaken on 43 of the sheep with a positive skin reaction. About 70% of sheep showed an immediate airway response to the antigen as an aerosol, reflected as a significant increase in airway resistance and/or decrease of dynamic lung compliance. The mean peak airway resistance and mean lowest dynamic lung compliance were 165% above and 61% below their baselines, respectively. No significant changes were recorded when the same animals were given an aerosol of phosphate buffered saline. Similarly, no correlation was found between the degree of skin reaction and the magnitude of bronchoconstriction (p>0.05). The sheep with previous exposure to pigs showed no significant differences in airway responses to antigen challenge, although they showed significantly greater skin reactions than those without exposure to pigs. These results indicate that the majority of Romney sheep in the Manawatu have a natural skin and airway sensitivity to A. suum antigen and may therefore be used as an animal model to study human airway hypersensitivity. The origin of this sensitivity has yet to be determined.

Journal Article↗
PubMed1990

Perinatal development of lymphoid tissue and its associated epithelium in the ovine pharyngeal tonsil: a morphological study.

The perinatal development of lymphoid tissue and its associated epithelium in the pharyngeal tonsil of sheep was investigated by light and electron microscopy. The lymphoid cells first appeared in the subepithelium in a scattered form at about 92 days gestation. These cells proliferated rapidly during the last trimester of gestation, and had formed many dense aggregates at the time of parturition. At birth, the epithelium overlying the aggregates was extensively infiltrated with lymphocytes and showed early transformation of follicle-associated epithelium. The lymphoid tissue and its associated epithelium did not, however, fully develop until after birth, when well-differentiated follicle-associated epithelium and lymphoid follicles with vigorous lymphopoiesis were present. In 1-2 week old lambs, these structures were ultrastructurally similar to those seen in adult sheep although their size was smaller. The results of this study suggest that the lymphoid tissue of the ovine pharyngeal tonsil and its associated epithelium are morphologically ready to cope with antigens in the extra-uterine environment at birth, but that their full development and maturation are dependent postnatal antigen stimulation.

Journal Article↗
PubMed1990

Chronic renal failure in young Old English Sheepdogs.

Chronic renal failure was diagnosed in three young Old English Sheepdogs. Clinical signs were characterised by ill-thrift, polydipsia, polyuria, nervous signs and behavioural changes. Laboratory findings showed azotaemia, non-regenerative anaemia, hyperphosphataemia and isosthenuria. The kidneys were characterised histologically by interstitial fibrosis, and thickening and calcification of the tubular and glomerular basement membrane. A familial incidence could not be confirmed in these cases.

Journal Article↗
PubMed1990

Effect of aerobic and resistance training on fractionated reaction time and speed of movement.

To evaluate the effect of aerobic and variable resistance exercise training on fractionated reaction time (RT) and speed of movement (SM) in elderly individuals, premotor time (PMT), motor time (MT), total RT, and SM were measured in 49 healthy, untrained men and women, 70 to 79 years of age, before and after 6 months of training. Subjects were randomized into either a walk/jog (n = 17), a strength training (n = 20), or a control group (n = 12). Improvements in aerobic capacity were only weakly related to reduced total RT (r = 0.30, p less than .05). Analysis of covariance revealed that there were no differences (p greater than .05) among the three groups after training with respect to PMT, MT, total RT, and SM. These findings indicate that 6 months of aerobic and strength training did not induce significant changes in RT or SM in this group.

Aged↗
PubMed1990

Mast cells in the ovine lower respiratory tract: heterogeneity, morphology and density.

The lower respiratory tract (LRT) of 6 adult sheep was fixed in either isotonic formalin-acetic acid or neutral buffered formalin in order to study the heterogeneity, morphology and density of mast cells (MCs). Two subtypes of MCs were found, one histochemically similar to connective tissue MCs (formalin resistant) and the other similar to mucosal MCs as found in the intestine of the rat (formalin sensitive). Although both subtypes were present at all levels of the tract, formalin-sensitive MCs were significantly more abundant (p less than 0.01) at all levels, and their density increased distally from the trachea to the peripheral lung. The formalin-sensitive MCs were predominantly located in the alveolar septa and in the superficial lamina propria of airways and less frequently within the airway epithelium. The MCs in the ovine LRT were found to be morphologically heterogeneous at both the light-microscopic and electron-microscopic levels. These findings indicate that ovine respiratory tract MCs have similarity to human lung MCs, and therefore potential for use as a model for the study of human allergic disease of the respiratory system.

Animals↗
PubMed1990

Selenium contents in human gallbladder bile.

The selenium contents in human gallbladder bile were analyzed. Thirty-seven subjects were studied; 22 patients with cholelithiasis in Niigata Prefecture and 15 patients (13 with cholelithiasis and 2 with gallbladder polypus) in Kochi Prefecture. Five ml of bile was withdrawn with a syringe from the gallbladder during the operation and stored at -20 degrees C until analysis. For the analysis by gas chromatograph with an electron-capture detector, 0.2 ml of sample was used. The mean selenium contents in bile were 269 +/- 39.0 (mean +/- S.D.) ng/ml for the subjects in Niigata and 285 +/- 84.4 ng/ml in Kochi; without significant difference. Of 37 samples analyzed, the mean content was 276 +/- 61.0 ng/ml.

Adult↗
PubMed1990

A case of zinc deficiency during long-term total parenteral nutrition.

A 54-year-old housewife received total parenteral nutrition (TPN) because of an intestinal fistula and total wound breakdown after an emergency operation for perforation of the ileum and diffuse peritonitis. The TPN regimen reversed the catabolism and resolved the abdominal wound and enterocutaneous fistula. Zinc and copper were not supplemented because there was no licensed parenteral trace element solution available. At week 17 of TPN, eczematoid dermatitis appeared on the face, nasolabial folds and chin, and the perineal area. These changes, coinciding with a serum zinc level of 20 micrograms/dl, were consistent with zinc deficiency. Zinc supplementation was commenced giving 6 mg of elemental zinc intravenously daily. The response to zinc therapy was very dramatic. Not only did the serum zinc level increase, but the skin changes returned to normal within 7 days. The patient gradually resumed her usual diet and TPN was discontinued after an approximate duration of 21 weeks. She was later discharged in good health.

Copper↗
PubMed1990

Computed tomography in the evaluation of pleural dissemination in lung cancer.

A total of 19 patients with lung cancer were recognized as unresectable or not curatively resectable at thoracotomy due to pleural dissemination during the period from January 1984 to March 1989. The computed tomography films of these cases were reviewed retrospectively to search for clues of early detection of pleural dissemination in order to avoid unnecessary exploration. The findings of the pleura in these 19 patients included: fine pleural nodules in 12 cases, pleural thickening in 11, pleural surface irregularity in 10, direct pleural attachment of the tumor in 8, pleural retraction by the tumor in 7, pleural effusion in 5, and chest wall invasion in 5. In this series, 15 out of the 19 cases had at least one of the following three findings: pleural thickening, pleural surface irregularity or pleural nodules. These pleural changes on a chest CT should raise the suspicion of pleural dissemination. An additional diagnostic procedure to establish diagnosis before exploration is suggested.

Adult↗
PubMed1990

[Diagnostic value of transbronchial lung biopsy in diffuse or peripheral lung lesions].

The results of 102 cases of diffuse or peripheral lung lesions examined by transbronchial lung biopsy (TBLB), bronchial brushing (BB), and bronchial alveolar lavage (BAL) via fiberoptic bronchoscope, were reported. The positive diagnostic rate was 74.5% (76 cases). In lung cancer, the positive rate by means of BB was 77.1%, which was higher than that by TBLB (58.1%). In pulmonary tuberculosis, the positive rate by TBLB was 76.9%, higher than that by BAL fluid for identification of tubercle bacillus by culture (44.4%). If TBLB was combined with BB and BAL, the positive diagnostic rate would be further elevated. The data showed that if the size of the masses greater than or equal to 3cm in peripheral lung field on chest film, the possibility of lung cancer was greater than that of those less than 3cm. Most cases of localized infiltration in the lungs were caused by tuberculosis. But the diffuse lesions of the lungs were often caused by bronchiolo-alveolar carcinoma, adenocarcinoma, diffuse interstitial fibrosis of the lungs, silicosis, sarcoidosis, etc. By the careful study of the chest film and ascertainment of the exact locations of the pulmonary lesions there, we can carry out the TBLB and obtain a satisfactory specimen without any X-ray monitoring. In the present group of patients who underwent TBLB, one was complicated by haemorrhage (greater than 50ml) and two by pneumothorax, but all of them recovered promptly after proper management. By strick adherence to indication, adequate preoperative preparations and very careful performance of the procedure, the complications of TBLB could be reduced to minimum.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1990

[Pest control and yield increase of areca by root-zone application of carbofuran in admixture with fertilizers].

The result of our experiment has shown that by root-zone application of carbofuran in admixture with fertilizers to Areca in spring the serious pest Tirathaba rufivena can be controlled for 4 months during flowering and young fruiting stage and the yield can increase by 50%. The final residual amount of carbofuran in fruits is below 0.1-0.01 ppm or too low to be examined, and there is no decrease in total alkaloid content in fruits.

Alkaloids↗