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Biomedical subjects

J Y Yuan

Publications and source records attributed to J Y Yuan.

14 recordsLinked to original sources
PubMed1998

Use of the appendix to replace the choledochus.

Ten cases of choledochal cyst (CC) were treated by biliary-appendicoduodenostomy. The follow-up comprised a patient interview, ultrasonography (US), and single-proton ejected computerized tomography (SPECT) scanning. In all cases an anti-reflux submucosal tunnel was added to the distal appendico-duodenostomy; all showed an uneventful postoperative course. All the dilated intrahepatic bile ducts had normalized on B-US postoperatively. Four children under went SPECT examination; all of them had patent neo-bile ducts. In the authors' opinion: (1) Anastomosing the cecal end of the appendix to the common hepatic duct seemed more favorable than the other way around, because the cecal end could be easily trimmed to the size of the common hepatic duct, which was more or less dilated in the presence of a CC; (2) It is necessary to add a submucosal tunnel to the distal appendicoduodenostomy to achieve a more reliable anti-reflux effect; and (3) Transposing the vascularized appendix through the retro-transverse colon simplified the procedure and might reduce the risk of retroperitoneal complications if bile leakage should occur.

Appendix↗
PubMed1998

Hydration force in the atomic force microscope: A computational study.

Using a hard sphere model and numerical calculations, the effect of the hydration force between a conical tip and a flat surface in the atomic force microscope (AFM) is examined. The numerical results show that the hydration force remains oscillatory, even down to a tip apex of a single water molecule, but its lateral extent is limited to a size of a few water molecules. In general, the contribution of the hydration force is relatively small, but, given the small imaging force ( approximately 0.1 nN) typically used for biological specimens, a layer of water molecules is likely to remain "bound" to the specimen surface. This water layer, between the tip and specimen, could act as a "lubricant" to reduce lateral force, and thus could be one of the reasons for the remarkably high resolution achieved with contact-mode AFM. To disrupt this layer, and to have a true tip-sample contact, a probe force of several nanonewtons would be required. The numerical results also show that the ultimate apex of the tip will determine the magnitude of the hydration force, but that the averaged hydration pressure is independent of the radius of curvature. This latter conclusion suggests that there should be no penalty for the use of sharper tips if hydration force is the dominant interaction between the tip and the specimen, which might be realizable under certain conditions. Furthermore, the calculated hydration energy near the specimen surface compares well with experimentally determined values with an atomic force microscope, providing further support to the validity of these calculations.

Calibration↗
PubMed1996

The effect of deformation on the lateral resolution of atomic force microscopy.

A computer model based on the elastic properties of rubber is introduced for the evaluation of the lateral resolution in atomic force microscopy of deformable specimens. The computational results show that, if the full width at half-height can be defined as the lateral resolution, it is continuously improved at greater probe forces, at the expense of a reduced molecular height, In fact, even for a probe that is bigger than the molecule, the real size of the molecule can be 'recovered' at about 25% compression. This result demonstrates that for a better lateral resolution, a greater probe force can be beneficial, provided that the molecule is not moved or damaged and the response remains elastic. Measurements on isolated low-density lipoproteins (LDL) show that with 26% vertical compression, the lateral size measured in atomic force microscopy is only 72% of the value predicted by a simple convolution, and is only slightly larger (approximately 13%) than the known size of LDL. Therefore, the results on LDL provide a direct support for the conclusions of the computational model.

Computer Simulation↗
PubMed1993

Primary hepatocellular carcinoma in women of mainland China. A clinicopathologic analysis of 104 patients.

The clinicopathologic characteristics of 104 hepatectomy samples from female patients with primary hepatocellular carcinoma (PHC) were compared with similar samples from 900 male patients with primary hepatocellular carcinoma; results of this comparison were studied. The male-to-female ratio was 8.7:1. The mean age of female patients with PHC was 46.2 years, which was approximately 3 years younger (49.1 years) than that of male patients with PHC. The frequency of associated liver cirrhosis (LC) was 49% in women with PHC and 68.2% in men with PHC (P < 0.01). The mean age of the female patients without LC was 43.2 years, more than 4 years younger (47.9 years) than that of the male patients. The mean ages of female and male patients with LC were 49.1 years and 49.8 years, 6 and 2 years older than that of their corresponding groups without LC, respectively. The positive rates of serum hepatitis B surface antigen (HBsAg) were 70.8% in the men and 59.7% in the women. The 5-year postoperative survival rates were 50% in the women and 25.7% in the men (P < 0.01). It is suggested that the development of PHC in women appears at a younger age than that of PHC in men in China and usually is associated with a lower frequency of LC and a more satisfactory postoperative prognosis.

Adult↗
PubMed1992

Regulation of 1 alpha, 25-dihydroxyvitamin D3 synthesis in macrophages from arthritic joints by phorbol ester, dibutyryl-cAMP and calcium ionophore (A23187).

Phorbol 12-myristate 13-acetate (100 nM), a potent protein kinase C and macrophage activator, has a biphasic affect on 25(OH)D3-1 alpha-hydroxylase activity in synovial fluid macrophages from arthritis patients. After 5 h, 1 alpha, 25(OH)D3 synthesis fell from 5.2 +/- 0.1 to 1.6 +/- 0.2 pmol/h per 10(6) cells, however, after 24 h and 48 h, synthesis increased to 17.4 +/- 0.3 and 22.3 +/- 1.4 pmol/h per 10(6) cells, respectively. Although an independent short-term mechanism is suggested, protein kinase C may promote macrophage activation, thus increasing long-term 25(OH)D3-1 alpha-hydroxylase expression. Intracellular calcium and cAMP are unlikely to activate the enzyme, since 0.1 microM of the calcium ionophore, A23187, and 1 mM dibutyryl-cAMP inhibited synthesis by 87% and 79%, respectively, after 24 h.

Arthritis↗
PubMed1991

Tc4, a Caenorhabditis elegans transposable element with an unusual fold-back structure.

We have identified and characterized a family of transposable elements in the nematode Caenorhabditis elegans. The Tc4 transposable element family is present at about 20 copies per haploid genome in the C. elegans Bristol and Bergerac strains. Although Tc4 transposition events have not been observed in these wild-type strains, we have identified Tc4 transposition events in the mut-2 mutant strain TR679, in which the elements Tc1 and Tc3 also transpose at a higher frequency than in the wild type. We determined the sequence of one Tc4 element. This 1.6-kilobase element contains almost perfect inverted terminal repeats of 774 base pairs (bp) with a 57-bp unique internal sequence. Tc4 is a fold-back element, but its long inverted terminal repeats, unlike those of the fold-back elements of other organisms, do not consist of multiple short repeats. In the two cases studied, Tc4 insertion resulted in duplication of a TNA trinucleotide target site. The family of Tc4 elements differs from other C. elegans transposable element families in structure, degree of structural heterogeneity, and target-site specificity.

Animals↗
PubMed1990

The Caenorhabditis elegans genes ced-3 and ced-4 act cell autonomously to cause programmed cell death.

Mutations in the genes ced-3 and ced-4 prevent almost all of the programmed cell deaths that occur during Caenorhabditis elegans development. To determine the sites of action of these two genes, we performed genetic mosaic analyses. We generated C. elegans animals that carried a free chromosomal duplication bearing either ced-3(+) or ced-4(+) in an otherwise homozygous ced-3 or ced-4 genetic background. We used other genes on the duplication as markers to identify genetic mosaic animals in which the duplication was present in some but not all cells. The patterns of cell death survivors in these mosaic animals indicated that the products of both ced-3 and ced-4 function within dying cells to cause cell death.

Animals↗
PubMed1990

[The coagulogram in patients with nephrotic syndrome].

The coagulogram done in half of the 100 cases of nephrotic patients admitted into our hospital from 1986 to 1988 was studied. It is shown that the patients of either the renal vein thrombosis (RVT) positive or negative group were in hypercoagulability state. 46 patients in this series had RVT proved by renography. The mechanism of RVT and the clinical significance of the changes of these hemostatic data are discussed.

Adult↗