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Biomedical subjects

Z Y He

Publications and source records attributed to Z Y He.

32 records · Page 2Linked to original sources
PubMed1995

Effects of antioxidants on fiber mutagenesis.

Recent studies from this laboratory have shown that asbestos fibers are mutagenic in cultured mammalian cells when assayed using a system that can detect multilocus deletions. Southern analysis of the induced mutants shows that the majority contain large deletions ranging in size from a few thousand to several million basepairs. In the present study, the effects of free radical scavenging enzymes on the cytotoxic and mutagenic potential of chrysotile fibers were examined using the human-hamster hybrid (AL) cells. Exponentially growing cells were treated with graded doses of fibers for a 24 h period either in the presence or absence of catalase, superoxide dismutase (SOD) or Tempol. Fiber-exposed cells were treated with the various enzymes either concurrently with the fiber or extended through the entire expression period. While the survival of AL cells treated with graded doses of chrysotile fibers with or without a concurrent treatment with SOD and catalase was not significantly different, the mutation yield at the S1 locus was significantly reduced in cells treated with these antioxidant enzymes. Furthermore, cells treated with the enzymes for a prolonged period were not better protected than those treated only during fiber treatment. The SOD mimic nitroxide, Tempol, had no effect on either the survival or mutagenic yield of chrysotile fibers. While SOD and catalase reduced the mutagenic potency of asbestos fibers in AL cells, they did not alter the molecular spectrum of fiber-induced mutagenesis. Our results indicate that antioxidant enzymes can protect cells against the genotoxic damages induced by chrysotile fibers, and are highly suggestive of the roles of oxyradicals in the fibrogenic and carcinogenic mechanisms of asbestos fibers.

Animals↗
PubMed1995

Effects of toquipidine on ionic channels of cultured embryonic Xenopus laevis myoblasts and neurons.

AIM: To study the effects of toquipidine (1-p-methyl-phenyl-2-(alpha-piperidinoacetyl)-1, 2, 3, 4-tetrahydroisoquinoline hydrochloride, Toq), a new anti-arrhythmic agent first synthesized in China, on ionic channels. METHODS: Ionic channel currents were recorded by whole-cell patch clamp technique in cultured embryonic Xenopus laevis myoblasts and neurons. RESULTS: Toq (0.1, 1, 10, and 100 mumol L-1) caused a concentration-dependent inhibition of the Na+ currents with IC50 7.2 mumol L-1 (5.3-9.8 mumol L-1). Toq (10 mumol L-1) also suppressed the high-voltage-activated Ca2+ currents in neurons. But the steady-state outward K+ currents in myoblasts were activated by Toq (10 mumol L-1). CONCLUSION: Toq blocked the Na+ and Ca2+ channels and opened the steady-state outward K+ channels.

Animals↗
PubMed1994

Time-varying adaptive filters for evoked potential estimation.

Adaptive implementation of an optimal time-varying filter (TVF) for evoked potential (EP) estimation is addressed in this paper. A data-adaptive scheme is used, which converges asymptotically to the optimal TVF solution. Two basic adaptive TVF's (ATVF's) are first introduced, namely least mean square (LMS) ATVF and recursive least-squares (RLS) ATVF. The latter converges much faster than the former. Since the basic ATVF's usually require a relatively large set of response trials to get a meaningful solution, a reduced-order ATVF is further presented and the corresponding LMS and RLS (including a fast RLS) adaptive algorithms are developed. To save memory, a truncated Fourier expansion is suggested to express approximately the time-sequenced weight-vectors of the ATVF's, resulting in a simplified reduced-order ATVF. Finally, extensive simulations are provided to confirm the superior performance of the ATVF's. The present ATVF's can be used as prefilters for latency-corrected average (LCA) processing to obtain more informative estimates of EP signals.

Adult↗
PubMed1994

Peak component latency-corrected average method for evoked potential waveform estimation.

A peak component latency-corrected average (PC-LCA) method consisting of three steps is presented for estimating the evoked potentials (EP) in the human brain. The present PC-LCA is essentially an alternative version of the original LCA method developed by McGillem et al. It first uses a time-varying adaptive filter as a preprocessor to suppress the ongoing EEG and to enhance the EP. Then, the statistics of mean latencies and amplitudes of the EP peak components are estimated by a peak detection and alignment procedure. The final waveform estimate is obtained by superimposing the estimated mean peak components on background information and subsequently fitting a truncated Fourier series using the fast Fourier transform (FFT). Consistent estimates of the EP peak component information are established based on asymptotic analysis of the PC-LCA. Finally, real-time implementation of the PC-LCA is considered, and the superior performance of the PC-LCA method is confirmed by detailed numerical results.

Electroencephalography↗
PubMed1993

The relationship between cytosolic free [Ca2+]i concentration and intracellular cAMP of platelet at various stages of experimental atherosclerosis in rabbits.

The relationship between cytosolic free [Ca2+]i and intracellular cAMP of platelet at various stages of experimental atherosclerosis in rabbits was studied. The results showed that the increase of [Ca2+]i was negatively correlated with the level of cAMP in cholesterol-fed rabbits (r = -0.667, P < 0.001) for 2, 4, 8 and 12 weeks. The viscosity of the whole blood at shear rates of 230.4/s and 5.76/s increased only in rabbits fed with cholesterol for 2 weeks, but the plasma viscosity increased in those fed for 2 and 4 weeks.

Animals↗
PubMed1992

Chrysotile fiber is a strong mutagen in mammalian cells.

Although chrysotile asbestos is a proven human carcinogen, several studies have concluded that these fibers are not mutagenic to cultured mammalian cells. We show here, on the other hand, that when tested using the AL cell system that detects both intragenic and multilocus mutations, chrysotile is indeed mutagenic and comparable in strength to that of gamma-rays. Southern analysis of the induced mutants shows that the majority contains large deletions ranging in size from a few thousand to several million base pairs. Results of our study demonstrate that, while chrysotile may be less durable in vivo than the amphibole fibers such as crocidolites and amosites, it can effectively create genetic damage involved in the cancer process.

Animals↗
PubMed1992

Mechanism of oncogenicity for bioreductive drugs.

The oncogenic transforming potential of a series of bifunctional bioreductive drugs were examined under either aerated or hypoxic conditions to assess the contribution of side chains or nitroreduced products toward their carcinogenic mechanisms. Both the cytotoxicity and transforming effects of these drugs increased as a function of dose under hypoxia. In air and at doses that resulted in comparable cell killing, RSU-1069 and RB-88716 were substantially more oncogenic than RSU-1164 or SR-4233. In nitrogen, the oncogenicity of SR-4233 as a function of survival increased, whereas the transforming effect for the aziridine-containing drugs, RSU-1969 and RB-88716, decreased. These data suggest that, among the drugs examined, the transforming moiety in air is largely a function of the alkylating aziridine group. In hypoxia, the reduction of the nitro-moiety to the corresponding active metabolites may be responsible for much of the transformation observed.

Animals↗
PubMed1990

Ultrastructural circadian variation of mast cells in the pinna of the mouse.

It has been found previously under the light microscope that there was a circadian variation in mast cell number in the pinna of mice. The mast cell number was increased at 18.00 h and decreased at 06.00 h. In the current study, 5 mice of each group were synchronized for 4 weeks with a standard lighting regimen (light: 06.00-20.00 h; dark: 20.00-06.00 h). Both pinnas of every mouse of each group were removed at 06.00, 12.00, 18.00 and 24.00 h, respectively. Under the electron microscope, it was observed that more degranulated mast cells were found at 06.00 h and more intact mast cells were visible at 18.00 h. It appeared that the mast cell numbers, decreased and increased under the light microscope, were due to mast cell degradation and regranulation. This finding suggests that a functional circadian variation exists in the mast cell under physiological conditions.

Animals↗
PubMed1990

Studies with bifunctional bioreductive drugs. I. In vitro oncogenic transforming potential.

The oncogenic transforming potential of a series of bioreductive drugs including RSU-1069 and its various alkyl-substituted derivatives, RB-7040, RB-88716, RSU-1164, and RB-88712, has been compared using the C3H 10T1/2 cell system. While the aziridine moiety at the terminal end of the side chain confers greater cytotoxicity to both the 2-nitroimidazole (RSU-1069) and the 5-nitrofuran (RB-88716), it also increases the oncogenic transforming potential of the drugs correspondingly. By substituting the aziridine ring with methyl groups, the cytotoxicity and oncogenicity of these bioreductive drugs decrease in a way that is proportional to the degree of methylation. A clear structure-activity relationship can be demonstrated from these methyl-substituted derivatives such that a tetramethyl-substituent (RB-7040) is much less cytotoxic and oncogenic than a dimethyl-substituent (RSU-1164). RB-7040, which has in vitro and in vivo sensitizing efficiency comparable to the parental compound RSU-1069, is roughly tenfold less cytotoxic and, at concentrations that achieve an in vitro enhancement ratio of 2.9, induces a transforming frequency that is indistinguishable from the spontaneous rate.

Animals↗
PubMed1989

Quantitative study of circadian variations in mast cell number in different regions of the mouse.

The tongue, pinna and dorsal skin of adult male C-1 mice were removed at 03.00, 06.00, 09.00, 12.00, 15.00, 18.00, 21.00 and 24.00 h, fixed in basic lead acetate and stained with Alcian blue-safranin or 0.5% toluidine blue. The mast cell numbers of these regions were counted and analyzed statistically by analysis of variance. It was found that there were circadian variations in the mast cell number in the tongue, pinna and dorsal skin. The difference between the minimum and maximum of circadian variation in mast cell number in all three regions was highly significant (p less than 0.01). Furthermore, the time points of the maximum and minimum of mast cell number varied between the different regions. The time point of the minimum in the tongue and pinna was at 06.00 h, whereas it was at 09.00 h in the dorsal skin. The time point of the maximum in the tongue and dorsal skin was at 21.00 h, but in the pinna it was at 18.00 h.

Animals↗
PubMed1989

[A correlative study of sex hormonal receptor status and mammographic appearance in primary breast cancer].

The relation between the sex hormonal receptor status and the mammographic appearance of the primary breast cancer in 162 patients was studied. The hormonal receptor status of breast cancer could be inferred by its shape and size as seen on the mammogram. The hormonal receptor level tended to be high tumors with prominent spiculate shadows or when the size of the tumor was small regardless of its shape, but lower in the majority of tumors which were large and lumpy with less hair-like projections or devoid of spicules. The mechanism of this phenomenon has been investigated. In addition, 119 patients with mammography taken of the opposite breast were analysed and no correlation was found between Wolfe's parenchymal pattern and hormonal receptor status. The authors suggested that mammography might be a simple and reliable method of assess the hormonal receptor status in breast cancer.

Breast Neoplasms↗
PubMed1989

[Investigation on an outbreak of allergic pulmonary alveolitis].

20 allergic alveolitis cases occurred abruptly within 10 days among teachers at a primary school in Shanghai. The cases make up 42.6% (20/47) of total staffs of the school. No patient discovered in pupils (137) though they had enough chance to contact with their teachers suffering the disease. Roentgenography and clinical findings were criteria of diagnosis. The findings of epidemiologic survey showed that the outbreak was caused by a single exposure of same agent, probably associated with sugarcane. The result of examinations in laboratory shows: 1. The content of IgE increased significantly in serum of convalescence patients. 2. Penicillium and Mucor were found as prevailing fungus strains benign isolated from the surface of sugarcane. 3. Did not find ascarid larva in sputum nor eggs in feces. In this paper we inferred reasonably that breathing of dust with fungus may be the cause of the outbreak.

Adult↗