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Y M Hu

Publications and source records attributed to Y M Hu.

At least 19 recordsLinked to original sources
PubMed1999

Intensity-modulation radiotherapy using independent collimators: an algorithm study.

The purpose of this work is to investigate algorithms for the delivery of intensity-modulated fields using independent collimators (IC). Two heuristic algorithms are proposed to calculate jaw-setting sequences for arbitrary 2D intensity distributions. The first algorithm is based on searching the whole intensity matrix to find the largest nonzero rectangular area as a segment while the second algorithm is to find a nonzero rectangular area as a segment which makes the complexity of the remaining intensity matrix minimum. After a sequence is obtained, the delivery order of all its segments is optimized with the technique of simulated annealing to minimize the total jaw-moving time. To evaluate these two algorithms, randomly generated intensity matrices and three clinical cases of different complexity have been tested, and the results have been compared with one algorithm proposed for MLC technique. It is shown that the efficiency of IC technique becomes increasingly lower than that of MLC technique, and the relative efficiency of two algorithms proposed here is related to machine dose rate and jaw speed. Assuming the prescribed dose is 200 cGY per fraction, machine dose rate is 250 MU/min, and jaw speed is 1.5 cm/s, the treatment can be delivered within about 20 min for all three cases with the first algorithm. The second algorithm requires longer delivery time under such assumptions. The delivery time can be further reduced through increasing machine dose rate and jaw speed, and developing more efficient algorithms. The use of IC for intensity-modulation radiotherapy has some potential advantages over other techniques.

Algorithms↗
PubMed1999

Prophylactic effects of tetramethyl pyrazine on mice with endotoxemia and its relationship with platelet-activating factor.

AIM: To study the prophylactic effects of tetramethyl pyrazine (TMP) on mice with endotoxemia and its relationship with platelet-activating factor (PAF). METHODS: LD80 of lipopolysaccharides (LPS, 15 mg.kg-1) was injected into mice (i.v.) pretreated with TMP (i.p.). The survival rate and the level of serum PAF were observed. The PAF induced by LPS in vivo and in vitro, and the activities of PLA2 and acetyl-CoA: lyso-PAF acetyltransferase were determined. RESULTS: TMP (10, 30, 90 mg.kg-1) obviously lowered the mortality of mice and also dose-dependently decreased the level of serum PAF [(25.5 +/- 1.7), (13.4 +/- 3.2), (9.6 +/- 2.1) micrograms.L-1, vs control (29.3 +/- 2.1) micrograms.L-1, P < 0.01]. TMP (0.05, 0.5, 5, 50 mumol.L-1) dose-dependently decreased the release of PAF [(12.7 +/- 1.6), (8.9 +/- 1.2), (6.9 +/- 0.8), (5.5 +/- 1.0) micrograms.L-1 vs control (11.9 +/- 1.8) micrograms.L-1, P < 0.01] from PMO cultured with LPS (5 mg.L-1), reduced the PLA2 activity [(149.9 +/- 2.8), (117.5 +/- 2.0), (89.6 +/- 2.0), (75.0 +/- 2.8) U vs control (170.8 +/- 3.9) U, P < 0.01] and acetyl-CoA: lyso-PAF acetyltransferase activity [PAF (9.5 +/- 0.7), (5.2 +/- 0.7), (2.9 +/- 0.3), (2.5 +/- 0.3) micrograms.g-1 (protein).min-1 vs control (11.0 +/- 0.7) micrograms.g-1 (protein).min-1, P < 0.01] of PMO lysate. CONCLUSION: TMP protected the mice with endotoxemia from the death by decreasing the biosynthesis of PAF through the inhibition of the activities of PLA2 and acetyl-CoA: lyso-PAF acetyl-transferase.

Acetyltransferases↗
PubMed1998

Protein synthesis is shutdown in dormant Mycobacterium tuberculosis and is reversed by oxygen or heat shock.

Oxygen-limiting conditions are critical to the survival of the bacteria in tuberculosis. Mycobacterium tuberculosis can survive anaerobiosis in vitro for long periods of time only after a gradual transition to a microaerophilic stationary phase. The underlying mechanism behind stationary phase adaption needs to be elucidated. The protein profiles of Mycobacterium tuberculosis during long-term stationary phase growth and under strict anaerobic incubation were monitored by [35S]methionine labelling, SDS-PAGE and fluorography. These experiments have established that protein synthesis gradually decreased over 50 days in the long-term stationary phase cultures which were considered to be microaerophilic. There was an 80% linear decrease in the level of total protein synthesis during the first 40 days of microaerophilic growth and then the rate of protein synthesis faded quickly. For the first time we have shown that total protein synthesis shutdown occurred when bacilli were incubated under further anaerobic conditions. Viability, estimated by cfu counts, remained constant during stationary phase growth and under anaerobic incubation. Furthermore, when oxygen was introduced into the anaerobic culture, protein synthesis restarted. Also heat shock at 45 degrees C, 48 degrees C and 50 degrees C rapidly induced protein synthesis in stationary and anaerobic cultures. These data indicate that dormant bacteria shut down protein synthesis but remain responsive to specific stimuli which restore protein synthesis. In addition the dormant bacilli induced by anaerobiosis developed more heat resistance than nondormant organisms.

Anaerobiosis↗
PubMed1998

Effects of nitroquine on ultrastructures and cytochrome oxidase of exoerythrocytic Plasmodium yoelii in rat liver.

AIM: To study the effects of nitroquine acetate (NA) on the ultrastructures and cytochrome-c oxidase (CCO) of exoerythrocytic forms (EEF) of Plasmodium yoelii. METHODS: Rats were inoculated with sporozoites directly into the liver. After 48 h rats were killed. Rat liver thin sections were incubated in histochemical reaction medium, then examined by transmission electron microscopy. NA (2 mg.kg-1) was fed to rats 3.5 h and 14 h before killing the rats. RESULTS: At 3.5 h, in the parasites there appeared swelling and proliferation of mitochondria, dilation of endoplasmic reticulum, and reduction of the electron density of parasites' nuclei. The structures of the parasites disintegrated to form many autophagocytes 14 h after exposure to NA. The reaction products of CCO still existed until 14 h after using NA. CONCLUSION: CCO was not the starting point of NA action. NA interferes with the structure and function of the cytoplasm and nucleus of malaria parasites and exerts its antimalarial effects in many aspects.

Animals↗
PubMed1998

Metronidazole has no antibacterial effect in Cornell model murine tuberculosis.

SETTING: Experiments in vitro on the bactericidal activity of metronidazole and in the Cornell model of murine tuberculosis. OBJECTIVE: To assess the sterilising activity of maximal metronidazole dosage and its activity against bacilli held dormant by immunity in the mouse. DESIGN: In vitro experiments showed that metronidazole was only bactericidal at attainable concentrations (50-100 microg/ml) under anaerobic conditions. In the Cornell model, isoniazid 25 mg/kg and high dosage pyrazinamide 1000 mg/kg was given in the diet with and without 1500 mg/kg metronidazole for the initial 14 weeks of sterilising chemotherapy. In the subsequent sterile state, metronidazole at 0, 100 and 250 mg/kg was given by daily gavage for 6 weeks. Finally, the mice were given 3 weeks of high dosage steroids and their organs were cultured in selective liquid medium. RESULTS: Metronidazole had no activity either in the initial sterilising phase or in the subsequent sterile state. CONCLUSION: The O2 tension in the cellular lesions of murine tuberculosis is unlikely to be sufficiently low to allow metronidazole to act. Its activity should be assessed in caseous lesions.

Animals↗
PubMed1997

[Effect of lysophosphatidylcholine on the pacemaker current I(f) of sheep cardial Purkinje fibers in ischemia-like condition].

By using two microelectrode voltage clamp technique, the effects of "ischemia" and lysophosphatidylcholine (LPC), a main toxic metabolite in acute ischemic myocardium, on pacemaker current I(f) were examined in sheep cardiac Purkinje fibers. After perfusion with ischemia-like solution for 15, 30 and 60 min, the amplitude of I(f) current was decreased at all membrane potential levels between -60 mV (-) -120 mV (n = 5, P < 0.05), both the activation time and half activation time reaching a steady state value were prolongated (n = 5, P < 0.05), with a result of shifting activation curve of I(f) to a more hyperpolarizing level. In normal Tyrode solution, the amplitudes of I(f) at all measured potential levels were decreased significantly by LPC 2 x 10(-5) mol/L (n = 10, P < 0.05); the steady-state activation curve of I(f) was shifted to a more hyperpolarizing level but the activation time and half activation time to a steady-state value were not changed. When 2 x 10(-5) mol/L LPC was added to the solution after 30 min "ischemia", the amplitude of I(f) decreased significantly at all measured membrane potentials and further more for another 15 min (n = 10, P < 0.05). This suggests that ischemic metabolite LPC may have an inhibitory effect on the normal pacemaker activity of ventricle. Ischemic-like condition could aggravate the suppression of LPC without inducing abnormal strengthening of normal automatic rhythmic activity that might lead to ventricular tachyarrhythmia.

Animals↗
PubMed1996

Protective effects of tetrandrine on CCl4-injured hepatocytes.

AIM: To study the protective effects of tetrandrine (Tet) on CCl4-injured hepatocytes. METHODS: The cultured rat liver cells were poisoned by CCl4 (10 mmol.L-1). The membrane fluidity was detected by 1,6-diphenyl-1,3,5-hexatriene (DPH), a lipid probe. The Ca2+ concentration was assayed with Fura 2-AM, a sensitive calcium indicator. RESULTS: Tet (1-1000 nmol.L-1) increased viability of liver cell (from 71% to 72%-89%), reduced lactate dehydrogenase (LDH) release, and malondialdehyde (MDA) formation. Tet prevented the heightening of the intracellular Ca2+ concentration and the attenuation of the membrane fluidity of liver cells (P < 0.05). CONCLUSION: Tet had a protective effect on CCl4-injured hepatocytes by inhibiting the lipid peroxidation, improving the membrane fluidity, and lessening the Ca2+ concentration.

Alkaloids↗
PubMed1996

Effects of tetrandrine, Fura 2-AM, and Bay k 8644 on platelet-activating factor release from rat peritoneal macrophages stimulated by lipopolysaccharides.

AIM: To study the relationship between the calcium and the release of platelet-activating factor (PAF) from rat peritoneal macrophages (PMø) stimulated by lipopolysaccharides (LPS). METHODS: The effects of tetrandrine (Tet), Fura 2-AM, and Bay k 8644 on the PAF release from rat PMø was investigated by the bio-assay of PAF. RESULTS: LPS stimulated PMø to release PAF, without increasing intracellular Ca2+ of PMø, Tet at 0.1, 1.0, 10, 100 mumol.L-1 and Fura 2-AM at 0.01, 0.1, 1.0, 10 mumol.L-1 could dose-dependently decrease the release of PAF (9.8 +/- 1.2, 6.5 +/- 1.6, 4.7 +/- 0.8, 3.4 +/- 0.4 microgram.L-1 and 9.2 +/- 1.7, 5.2 +/- 1.3, 3.7 +/- 0.4, 3.2 +/- 0.3 microgram.L-1, respectively, no drugs 11.8 +/- 1.2 micrograms.L-1), Bay k 8644 at 1.0, 5.0, 10 mumol.L-1 could dose-dependently increase the release of PAF (13.2 +/- 1.7, 16.2 +/- 1.4, 17.6 +/- 1.5 micrograms.L-1), and the effects of Tet and Fura 2-AM were completely or partly reversed by Bay k 8644 at 5.0 mumol.L-1. CONCLUSION: Although LPS did not increase intracellular Ca2+ of PMø, intracellular Ca2+ was necessary for PAF release from rat PMø stimulated by LPS.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1996

Effects of Coriolus versicolor polysaccharides peptides on electric activity of mediobasal hypothalamus and on immune function in rats.

AIM: The nervous mechanism of the immune potentiating effect of Coriolus versicolor polysaccharides peptides (PSP) was studied in Wistar rats. METHODS: The unit discharge of the mediobasal hypothalamus (MBH) neurons was recorded extracellularly and the lymphocyte proliferation was measured. RESULTS: PSP 1 g.kg-1 ig for 5 d increased the T-lymphocytes and promoted T-lymphocyte proliferation in spleen and peripheral blood. This promoting effect of PSP was blocked by MBH lesion. PSP increased the discharge frequency of MBH neurons, but no increase in discharge frequency was observed after treatment of PSP plus immune inhibitor, cyclosporin A. CONCLUSION: MBH is involved in the immune-potentiating effect of PSP.

Adjuvants, Immunologic↗
PubMed1994

Spontaneous rupture of the liver associated with pregnancy: a report of two cases.

Spontaneous rupture of the liver associated with pregnancy is a rare and grave complication, usually occurring in preeclampsia or eclampsia. Two cases of ruptured subcapsular hematoma of the right liver during pregnancy are reported. The first case was a 19-year-old woman who had suffered from epigastralgia and absent fetal heart beat in the 32nd week of gestation. The second case was a 31-year-old female who complained of nausea and right upper quadrant pain in the 35th week of pregnancy. Both had preeclampsia, and developed shock with disseminated intravascular coagulation soon after admission. Both received surgery and were found to have ruptured hematoma over the right liver. Finally, the first patient died of renal failure, but the second survived because preoperative diagnosis had been exact. Greater suspicion, then awareness of diagnosis can lead to better timing of surgery and an improved prognosis for mother and child.

Adult↗
PubMed1993

[Effects of four drugs on intraerythrocytic Plasmodium yoelii of early and late stages].

Erythrocytes of mice infected with Plasmodium yoelii of early stage (ESP) were separated from those infected with late stage (LSP), by a single density-gradient centrifugation in 19% diatrizoate meglumine. After centrifugation, the differential counts of ESP and LSP were 84.9% and 87.4%, respectively. The stage-dependent effects of nitroquine (NQ), pyrimethamine (Pyr), perphenazine (Per) and metronidazole (Met) were studied with [3H]adenosine incorporation into ESP and LSP in vitro using chloroquine (CQ) as control. Like CQ, the 4 drugs inhibited that [3H]adenosine incorporation into LSP more remarkably than that into ESP. The IC50 of CQ, Met, Pyr, Per, and NQ against ESP were 1.89, 2.11, 2.56, 2.60, and 4.65 times as high as that against LSP, respectively.

Animals↗
PubMed1992

[Effects of dexamethasone and cyclophosphamide on development of exo-erythrocytic form of Plasmodium cynomolgi bastianellii in rhesus monkey].

The rhesus monkeys (Macaca mulatta) challenged with Plasmodium cynomolgi bastianellii sporozoites were treated with im dexamethasone (Dex) 1 mg.kg-1.d-1 x 7 d and cyclophosphamide (Cyc) 25 mg.kg-1.d-1 x 3d, respectively. On d 7 after challenge, serial sections of liver biopsy stained with HE revealed that the distributive density and size of exo-erythrocytic (EE) form of the parasites showed no difference between medicated and control monkeys. The prepatent period of the primary attack and the relapse patterns after the treatment of Dex and Cyc were also similar to each other. The radically cured monkeys challenged with the Plasmodium erythrocytic form were reinfected with sporozoites, the relapses were much less than those in control monkeys, but the density and size of EE form in liver were similar to those in control monkeys. These results suggest that Dex and Cyc exert no effect on the development of EE form (including hypnozoite) in the monkeys.

Animals↗
PubMed1991

[Clinical significance of human basophil releasability in bronchial asthma].

Human basophil releasability (HBR) was determined in 50 patients with asthma by modified human basophil degranulation test (HBDT). The result of HBDT was expressed as degranulation index (DI). 1. Anti-IgE-induced HBR: the mean value of DI in extrinsic asthma, intrinsic asthma and control subjects was 50.1 +/- 2.26(%), 32.2 +/- 2.3(%) and 18 +/- 2.74(%) (x +/- sem) respectively. If a DI of 30% or greater was considered as positive, the positive rate in the above three groups would be 96.9%, 60.0% and 20.0% respectively. There was significant difference between any two of the three groups (P less than 0.01). 2. Allergen-induced HBR: HBDT was performed in the asthmatics with sixteen allergens and in the controls with mite allergen. The positive rates were 68% in the patients and 0% in the controls. The coincident rate of the results between HBDT and skin test reached 82.9%. The results showed that anti-IgE-induced HBR could be regarded as an objective parameter for differentiating extrinsic and intrinsic asthma and allergen-induced HBR could be considered as an useful means for in vitro allergen diagnosis of asthma.

Adolescent↗
PubMed1991

[Effect of nitroquine on protein synthesis of Plasmodium yoelii in vitro].

The erythrocytic stages of Plasmodium yoelii (BY 265 strain) were incubated with nitroquine (0.2 pmol.L-1 - 20 mumol.L-1), cycloheximide (0.1-10 nmol.L-1) and aminopterin (0.2 pmol.L-1 - 20 mumol.L-1) during 8 h in vitro. The results showed that the incorporation of [3H]-isoleucine into the protein by Plasmodium yoelii was inhibited by nitroquine (0.2 pmol.L-1) and cycloheximide (0.1 nmol.L-1), the inhibitory effect of nitroquine (IC50 = 0.16 nmol.L-1) was 397 times higher than that of cycloheximide (IC50 = 63.5 nmol.L-1). However, the incorporation of [3H]isoleucine into protein was not affected during at least 8 h of exposure to aminopterin (20 mumol.L-1). The results suggest that the inhibition of protein synthesis by nitroquine is one of the mechanisms of the early antimalarial action.

Aminopterin↗
PubMed1989

[Effects of nine prescriptions on fever in rats induced by endotoxin].

In this paper in is reported that nine prescriptions often used in traditional Chinese medicine for the treatment of diseases with fever were tested experimentally for the effect on fever of rats induced by endotoxin. The results are as follows: Da-yuan-decoction, Gan-lu-xiao-du-pill, Lian-pu-decoction, Cai-hao-mixture, Da-huang-huang-lian-jie-du-decoction, Tao-ren-cheng-qi-decorction, Ge-gen-qin-lian-decoction, Yin-qiao-jie-du-decoction etc. can notably reduce fever in rats induced by endotoxin with the exception of Bai-hu-decoction that has no obvious effect on fever-reduction.

Animals↗
PubMed1989

[The primary study on purification, characterization and function of rabbit serum HDL].

Rabbit serum HDL was isolated by gradient ultracentrifugation, found to be pure on PAGE, and characterized by PAGIF. The effect of HDL on normal and hyperlipidemic uptake of LDL into SMC through LDL receptors in rabbits was observed in three experiments. The percentage decrease between normal groups with and without HDL was small (2.3%, 5.5%, 7.3%), while the percentage decrease between hyperlipidemic groups with and without was large (23%, 25%, 26%). The results demonstrate that HDL affects the uptake of hyperlipidemic LDL into SMC through LDL receptors. This suggests that HDL might regulate the cholesterol overloading in cells in cases of hyperlipidemic LDL. The mechanism of HDL action is discussed.

Animals↗