PubMed Health⌕ Search

Biomedical subjects

C H Yan

Publications and source records attributed to C H Yan.

At least 37 records · Page 2Linked to original sources
PubMed1998

A new frame-based registration algorithm.

This paper presents a new algorithm for frame registration. Our algorithm requires only that the frame be comprised of straight rods, as opposed to the N structures or an accurate frame model required by existing algorithms. The algorithm utilizes the full 3D information in the frame as well as a least squares weighting scheme to achieve highly accurate registration. We use simulated CT data to assess the accuracy of our algorithm. We compare the performance of the proposed algorithm to two commonly used algorithms. Simulation results show that the proposed algorithm is comparable to the best existing techniques with knowledge of the exact mathematical frame model. For CT data corrupted with an unknown in-plane rotation or translation, the proposed technique is also comparable to the best existing techniques. However, in situations where there is a discrepancy of more than 2 mm (0.7% of the frame dimension) between the frame and the mathematical model, the proposed technique is significantly better (p < or = 0.05) than the existing techniques. The proposed algorithm can be applied to any existing frame without modification. It provides better registration accuracy and is robust against model mis-match. It allows greater flexibility on the frame structure. Lastly, it reduces the frame construction cost as adherence to a concise model is not required.

Algorithms↗
PubMed1998

Effects of dl-3-n-butylphthalide on regional cerebral blood flow in right middle cerebral artery occlusion rats.

AIM: To study the effect of dl-3-n-butylphthalide (NBP) on regional cerebral blood flow (rCBF) in forcal cerebral ischemia rats. METHODS: In chloral hydrate-anesthetized rat, the proximal portion of right middle cerebral artery (RMCA) was occluded, and H2 needle electrode was implanted in right striatum. rCBF was monitored in striatum using hydrogen clearance method. RESULTS: Ten min after RMCA occlusion (RMCAO), NBP (5, 10, 20 mg.kg-1 i.p.) markedly increased rCBF to striatum (P < 0.01). When NBP was given i.p. 40 min after RMCAO, the increasing effect on rCBF was also observed (P < 0.05). However, when NBP was injected i.p. 60 min after RMCAO, the increasing effect of NBP on rCBF was not found. In NBP-pretreated (i.p. 40 min before RMCAO) group, rCBF in striatum measured at different time points of 30, 60, 90, 120, 150, and 180 min after RMCAO were increased by 97%, 107%, 136%, 211%, 173%, and 317%, respectively, compared with the percentages of vehicle group. The potency of the effect of Nim (0.5 mg.kg-1 i.p.) was similar to that of NBP (10 mg.kg-1 i.p.). CONCLUSION: NBP pre-treatment or post-treatment markedly enhanced the rCBF to striatum in RMCAO rats.

Animals↗
PubMed1997

[Protective effects of D-3-N-butylphthalide and L-3-N-butylphthalide on neuronal damage induced by KCl and NMDA in cultured rat cortical neurons].

The protective effects of l-3-n-butylphthalide (l-NBP) and d-3-n-butylphthalide (d-NBP) on KCl (20 mmol.L-1)- or NMDA (N-methyl-D-aspartate, 30 mumol.L-1)-induced cytotoxicity in primary cultured rat cortical neurons were studied. Intracellular LDH release, percentage of cell death and cellular morphological changes were used to evaluate the effect of drugs. l-NBP (1-100 mumol.L-1) and d-NBP (1-100 mumol.L-1), but not nimodipine (1-100 mumol.L-1), were shown to dose-dependently inhibit LDH release induced by NMDA (30 mumol.L-1) in cultured rat cortical neurons with IC50 values of 4.89 mumol.L-1 and 13.52 mumol.L-1, respectively. The percent cell death was reduced with IC50 values of 44.37 and 49.78 mumol.L-1, and the cellular morphology improved. The effect seemed to be the same as that of equal concentration of NAME(NG-nitro-L-arginine methyl ester). In addition, l-NBP(10 mumol.L-1), d-NBP (10 mumol.L-1) and nimodipine(10 mumol.L-1) also produced significant inhibition on intracellular LDH release and decrease in percent cell death induced by KCl(20 mmol.L-1) in cultured neurons. The potencies of l-NBP and d-NBP were similar to that of equal dose of nimodipine. These data suggest that l-NBP and d-NBP can remarkably protect cultured neurons against the damage induced by KCl and NMDA.

Animals↗
PubMed1997

Umbilical cord blood lead levels in Shanghai, China.

This study was designed to determine the cord blood lead (BPb) levels of babies born in one urban area of Shanghai, and to preliminarily identify the demographic, social environment and prenatal factors which have an effect on the cord BPb concentrations. From August to November 1993, umbilical cord blood samples were obtained from 605 live newborns in the Yangpu Maternal and Child Hospital. 257 samples were excluded from measurement because of clotting. In 348 cord samples, the geometric mean of cord BPb levels was 9.2 micrograms/dl, with a 95% confidence interval of the mean 8.86-9.54 (micrograms/dl). 142 babies (40.8%) had cord BPb levels of 10 micrograms/dl or greater. As a result of this high percentage of newborns with BPb levels equal to or greater than 10 micrograms/dl, we estimate that each year in the Shanghai City about 60,000 newborns are at risk for developing neuropsychological deficiencies caused by maternal lead exposure during pregnancy. To investigate the factors affecting cord blood levels, the subjects with levels greater than the 70th percentile (10.7 micrograms/dl) (n = 104) and less than the 30th percentile (7.4 micrograms/dl) (n = 104) were selected to compare the demographic, environment and prenatal medical history. Increased BPb levels at birth were associated with maternal passive smoking, a family member being occupationally exposed to lead, proximity to major traffic way, household coal combustion, neighborhood coal combustion, low level of maternal occupations, and the increasing occurrence of having the high lead foodstuff pidan (preserved duck egg) during pregnancy. We conclude that prenatal lead exposure has become an important health issue for young children in Shanghai.

Adult↗
PubMed1995

Differential effects of 2,4-dithiobiuret on the synthesis and release of acetylcholine and dopamine from rat pheochromocytoma (PC12) cells.

Chronic administration of 2,4-dithiobiuret (DTB), causes delayed-onset neuromuscular weakness in rats. This effect results from inhibition of quantal release of acetylcholine (ACh) from motor nerve terminals. The effects of noncholinergic neurotransmission are unknown. The purpose of the present study was to examine the presynaptic mechanisms involved in DTB-induced inhibition of ACh release, particularly, the specificity of action of DTB for cholinergic secretion. Differentiated pheochromocytoma (PC12) cells were used to compare the effects of DTB on the content and release of ACh and dopamine (DA) using neurochemical techniques. At concentrations of 50 to 1000 microM, DTB had little or no effect on [3H]choline uptake or on the spontaneous release of endogenous or [3H]ACh, but caused a significant decrease in release of endogenous or [3H]ACh elicited by depolarization with elevated extracellular [K+]. DTB reduced evoked release of ACh without altering cellular levels of ACh or choline, suggesting that DTB acts directly on mechanisms involved in ACh release. These alterations occurred without prominent alterations in [Ca2+]i as measured by fluorescence microscopy of individual PC12 cells loaded with fura-2. Moreover, DTB did not affect the increase of [Ca2+]i of PC12 cells in response to KCl-induced depolarization. alpha-Latrotoxin-stimulated release of ACh was not inhibited by DTB. DTB-induced suppression of depolarization-evoked release of [3H]ACh was associated with an increased level of [3H]ACh in the vesicular pool although the cytosolic pool was unaffected. High concentrations of DTB also reduced depolarization-evoked release of DA and inhibited DA synthesis resulting in a decrease in the readily releasable pool of DA. These effects occurred at higher concentrations and after longer exposures to DTB than were necessary to alter ACh release. Inasmuch as DA synthesis in the PC12 cell has been shown to be modulated by ACh release, this effect on DA release may reflect a consequence of the diminished release of ACh. These results suggest that DTB alters the release of ACh by interrupting either the mobilization and/or release of the vesicular pool of ACh.

Acetylcholine↗
PubMed1994

[Reference values for blood, hair, and organ selenium levels in adults of Beijing].

Two hundred and four blood specimens and 202 hair specimens, and 72 tissue specimens of heart, liver, spleen, lung, kidney, muscle and skeleton from adults living in Beijing suddenly died were collected during 1990-1991. Selenium levels were determined by 2,3-diamine naphthalene fluorescence method with serum, human hair and calf liver as standard references to assure the quality of determination, and their reference values for adults in Beijing were established. Selenium nutritional status of the adults was evaluated preliminarily. Dietary selenium intake was estimated based on serum selenium levels, and the body total selenium content was estimated by biological monitoring.

Adolescent↗
PubMed1994

[Effects of methylflavonolamine hydrochloride on tension and cAMP of isolated guinea pig trachea].

Effects of methylflavonolamine (4'-methyl-7-(2-hydroxy-3-isopropylaminopropoxy)-flavone hydrochloride, MFA) on the tension and cAMP content of isolated guinea pig tracheal smooth muscle strips were studied. MFA (0.03-0.6 mmol.L-1) dose-dependently reduced KCl, acetylcholine (ACh) and histamine (Hist)-induced contractions with intracellular increase in cyclic AMP. The reduction in contraction and increase in cAMP were well correlated positively. MFA (0.03 mmol.L-1) showed synergism with isoprenaline (Iso) and aminophylline (Ami) in bronchodilation. The synergism with Iso but not Ami was accompanied by an increase in cAMP levels. It is suggested that the MFA-induced bronchodilation is related to the increase in intracellular cAMP level. The calcium antagonistic effect may be involved in MFA-induced bronchodilation.

Aminophylline↗
PubMed1992

[Effects of methylflavonolamine hydrochloride on contractility of isolated rabbit ileum].

Methylflavonolamine hydrochloride (MFA), verapamil (Ver), and trifluoperazine (Tri) inhibited the contractions induced by submaximal concentrations of acetylcholine (ACh) and serotonin (5-HT). IC50 values (mumol.L-1) were 33.2 +/- 0.7, 0.276 +/- 0.018, 3.83 +/- 0.23, and 15.31 +/- 0.10, 0.233 +/- 0.017, 2.33 +/- 0.20, respectively. MFA, Ver, and Tri inhibited the contractions induced by CaCl2 and pD'2 values were 4.3 +/- 0.3, 6.23 +/- 0.22, 4.99 +/- 0.24, respectively. MFA 3 mumol.L-1, Ver 0.03 mumol.L-1, and Tri 3 mumol.L-1 inhibited the contractions induced by ACh in Ca(2+)-free medium, while MFA 60 mumol.L-1, Tri 30 mumol.L-1, but not Ver 0.6 mumol.L-1, had pronounced inhibitions on extracellular calcium-dependent contractions induced by ACh. These results suggest that MFA has a calcium antagonistic effect and that MFA is similar to Tri, but not Ver, in mechanism.

Animals↗
PubMed1991

Spontaneous coronary artery dissection in a young man with anterior myocardial infarction.

A case of spontaneous coronary artery dissection in a young male with subsequent myocardial infarction is reported. In addition, distal vessel occlusion is noted, presumably from embolization of thrombotic material originating from the site of dissection. Postulated mechanisms of this uncommon cause of myocardial infarction and subsequent therapeutic options are reviewed.

Adult↗
PubMed1991

Anticancer gelatin microspheres with multiple functions.

Biodegradable, hydrophilic gelatin microspheres (GM) with an average diameter of 70 microns were prepared by cross-linking gelatin with glutaraldehyde for hepatic intra-arterial infusion. An anticancer agent, mitomycin C (MMC), together with a radioisotope, 131I, were bound to the GM for chemotherapy and local internal radiotherapy. The 131I-labelled MMC-GM (131I-MMC-GM) could accumulate in the specific site and embolize the hepatic arteries after the hepatic intra-arterial infusion, while it caused various effects to the liver cells. The 131I-MMC-GM remained within the hepatic arteries for at least one month. In vitro release of drugs from the GM was also quantified using a dynamic dialysis method.

Animals↗
PubMed1989

Direct examination of chemical kinetic laws by visual imagery. IV. Association processes between antigen- and fragmented antibody carrying fluorescent latex particles.

The binary association process was further examined by direct visual observation using a fluorescence microscope connected to an image-processing system and by a spectrophotometric method. In the present paper, we used human serum albumin (HSA)- and fragmented anti-HSA antibody-carrying fluorescent latex particles in order to attain higher sensitivities and exclude complexities that might be caused by dissociation of the association product. The rate constant of the binary association process was estimated to be 6.0 x 10(8) M-1 s-1 at 30 degrees C and pH 7.6. The activation parameters of the association process were evaluated. The effects of pH and viscosity of the suspension on the association process were also examined.

Antigen-Antibody Complex↗
PubMed1989

[The significance of mummy cell in the diagnosis of Hodgkin's disease].

The mummy cell is a necrotic single cell in lympho-reticular lesion, and it is characterized by the pattern of distributing isolated in a lympho-reticular background without detachment from the surrounding cells, staining deeply or amphibic in mature both nuclei and cytoplasm and the ghost nuclei are often recognized. Totally, 95 lympho-node biopsies were reviewed, the mummy cells can be found in 21/24 of Hodgkin's disease and 18/71 of other lesions (NHL, reactive hyperplasia etc.). They are more common in nodular sclerosis (NS) and lymphocyte depletion (LD) among the four subtypes of Hodgkin's disease. It is worthwhile to note the suggestive role of mummy cells in pathological diagnosis of Hodgkin's disease.

Hodgkin Disease↗
PubMed1989

[Blood gas analysis of varicocele, spermatic vein and peripheral vein].

Blood gas analysis was carried out in 80 cases of varicocele. The PO2 of the spermatic vein was lower than that of peripheral vein (P less than 0.01). There was also a significant difference of PO2 between I. and III. of varicocele (P less than 0.05). Blood of the spermatic vein showed metabolic acidosis. It is suggested that hypoxemia of the testes may affect spermatogenic function.

Adolescent↗