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Biomedical subjects

Z Han

Publications and source records attributed to Z Han.

At least 127 records · Page 7Linked to original sources
PubMed1996

[Malignant fibrous histiocytoma of kidney].

Malignant fibrous histiocytoma of kidney is one kind of rare tumor. About 20 cases have been reported abroad and 3 in this country. This kind of tumor is characterized by high malignancy and invasive growth. It is difficult to differentiate it from renal cancer by radiology. Fibroblasts stand in line as "storiform pattern" and touton giant cell can be seen under microscopy. The definite diagnosis can be made through immunohistochemistry.

Histiocytoma, Benign Fibrous↗
PubMed1995

Proliferative response of mammary glandular tissue to formononetin.

Dietary phytoestrogens have been implicated in infertility among ruminants and may relate to human breast cancer risk. Formononetin is an isoflavonoid phytoestrogen found in animal fodder and in certain human foodstuffs. To investigate a possible mechanism by which phytoestrogens might influence mammary carcinogenesis, this study examined the capacity of formononetin to stimulate mammary gland proliferation. Formononetin was administered to castrated female BALB/c mice by daily subcutaneous injection; then mammary gland proliferation and estrogen receptor expression were quantified, and plasma prolactin levels were measured. A preliminary dose-finding study demonstrated an estrogenic effect on vaginal cytology when formononetin was injected at 40 mg/kg sc. Peak plasma concentrations of 2.5 +/- 0.8 (SD) micrograms/ml at two hours and peak mammary tissue concentrations of 2.0 +/- 0.2 ng/mg tissue at four hours were noted after a single injection at this minimally bioactive dose. Among animals treated with formononetin at 40 mg/kg/day for five days, mammary gland proliferation was enhanced 3.3-fold over saline-treated controls and was comparable to that of animals treated with estradiol-17 beta at 1 microgram/kg/day for five days. Mammary tissue estrogen receptor expression was 2-fold higher among the formononetin-treated animals (P < 0.01 vs. saline-treated controls), and plasma prolactin concentrations were increased 1.7-fold (P < 0.001 vs. saline-treated controls). In subsequent in vitro binding studies, formononetin competitively bound murine mammary estrogen receptors, but with a relative binding affinity 15,000 times less potent than that of estradiol-17 beta. The results demonstrate an ability of formononetin to support mammary gland proliferation. However, the estrogenic potency of formononetin appears extremely weak compared with that of estradiol-17 beta and is roughly proportional to estrogen receptor-binding capacity.

Animals↗
PubMed1995

Evidence for a G2 checkpoint in p53-independent apoptosis induction by X-irradiation.

The p53 tumor suppressor gene is thought to be required for the induction of programmed cell death (apoptosis) initiated by DNA damage. We show here, however, that the human promyelocytic leukemia cell line HL-60, which is known to be deficient in p53 because of large deletions in the p53 gene, can be induced to undergo apoptosis following X-irradiation. We demonstrate that the decision to undergo apoptosis in this cell line appears to be made at a G2 checkpoint. In addition, we characterize an HL-60 variant, HCW-2, which is radioresistant. HCW-2 cells display DNA damage induction and repair capabilities identical to those of the parental HL-60 cell line. Thus, the difference between the two cell lines appears to be that X-irradiation induces apoptosis in HL-60, but not in HCW-2, cells. Paradoxically, HCW-2 cells display high levels of expression of bax, which enhances apoptosis, and no longer express bcl-2, which blocks apoptosis. HCW-2 cells' resistance to apoptosis may be due to the acquisition of expression of bcl-XL, a bcl-2-related inhibitor of apoptosis. In summary, apoptosis can be induced in X-irradiated HL-60 cells by a p53-independent mechanism at a G2 checkpoint, despite the presence of endogenous bcl-2. The resistance shown by HCW-2 cells suggests that bcl-XL can block this process.

Apoptosis↗
PubMed1995

[The pathogenetic factors for neurogenic intermittent claudication caused by degenerative lumbar spinal stenosis].

The pathogenetic factors in 89 patients with typical neurogenic intermittent claudication caused by lumbar spinal stenosis were studied retrospectively. 75 patients had degenerative lumbar spinal stenosis, and 67 had unilateral nerve root canal stenosis. In most patients, the stenotic location was found at the entrance zone of nerve root canal (75/89), involving only a single level (60/89) mostly at L4.5. The pathogenetic factors for degenerative lumbar spinal stenosis were degenerative changes of lumbar disc only (55/89), and those for hypertrophy of facet joints (22/89), thickened ligamentum flavum (11/89), and spondylolis thesis (10/89). All patients were operated on: 57 of them had less invasive procedures. The excellent and good early follow-up results were noted in 73% of the patients (65/89). The authors emphasized that the surgical treatment of lumbar spinal stenosis should be as less invasive as possible rather than a tranditional extensive lumbar laminectomy.

Adult↗
PubMed1995

A study on oliguric standard in the elderly.

Water deprivation test was done in 44 healthy elderly persons, 26 were male, and 18 were female. They were deprived of the intake of water for 25 hours. The results showed that the maximal renal concentration function both in the elderly males and females was 887 +/- 91 mmol/L and 888 +/- 127 mmol/L respectively. The renal excretion of waste products in 24 hours both in the elderly males and females was 815 + 170 mmol/d and 620 + 132 mmol/d respectively. On the basis of point estimation, the minimal essential urine volume per day in the elderly males and females was 926 ml/d and 708 ml/d respectively, if the daily urine volume of the elderly is less than this level, then, the metabolic products generated per day can not be excreted by the kidney, and it would result in disorders of internal environment. Therefore, the oliguric standard in elderly males and females must be less than 926 ml/d and 708 ml per day respectively.

Age Factors↗
PubMed1995

[Influence of thoracic spinal subarachnoid microinjection of noradrenaline on the effect of electroacupuncture].

Influence of thoracic spinal subarachnoid microinjection of noradrenaline (NA, 40 mg/20 microliters) on the effect of electroacupuncture (EA) at Neiguan (PC6) was observed in 40 rabbits anesthetized with urethan-chloralose. Results showed that: 1) EA of Neiguan (PC6) could significantly accelerate the recovery of ST-segment and T-wave of electrocardiogram induced by acute myocardial ischemia (AMI); 2). Subarachnoid microinjection of NA also could promote the recovery of ST, T and blood pressure of post-AMI; and 3) Subarachnoid microinjection of NA could strengthen the effect of EA of Neiguan (PC6) to promote the recovery of ST and T of Post-AMI. It suggests that alpha-receptors of intra-thoracic spinal cord participate in the action of EA of Neiguan (PC6) ameliorating AMI, and the upper thoracic segement is one of the links for connecting Neiguan and the heart.

Acupuncture Therapy↗
PubMed1994

Three chemically distinct types of oxidants formed by iron-mediated Fenton reactions in the presence of DNA.

Exposure of Escherichia coli to H2O2 leads to two kinetically distinguishable modes of killing: mode I killing occurs maximally near 2 mM H2O2, whereas mode II killing is essentially independent of H2O2 concentrations up to 20 mM. A major portion of H2O2 toxicity is attributed to DNA damage caused by the iron-mediated Fenton reaction. By studying DNA damage during Fenton reactions in vitro, the same complex kinetics were observed and three types of oxidants were distinguished based upon their reactivities toward H2O2 and alcohols and upon iron-chelator effects. Type I oxidants are sensitive to H2O2 but moderately resistant to ethanol; type II oxidants are resistant to both H2O2 and ethanol; type III oxidants are sensitive to H2O2, ethanol, and t-butanol. To explain these results, we hypothesize that type I oxidants are generated upon Fe2+ associated with DNA only through electrostatic interactions and cause mode I killing of E. coli; type II oxidants arise upon Fe2+, which is at least partially base-associated, and cause mode II killing; type III oxidants arise on Fe2+ free in solution and probably do not cause killing. Therefore, particular interactions of DNA with transition metals should be considered to be an integral part of the chemistry and toxicity of H2O2.

DNA↗
PubMed1994

Analysis of Schizosaccharomyces pombe mitochondrial DNA replication by two dimensional gel electrophoresis.

The entire mitochondrial genome of Schizosaccharomyces pombe ura4-294h- was analyzed by the 2D pulsed field gel electrophoresis technique developed by Brewer and Fangman. The genome consists of multimers with an average size of 100 kb and analysis of the overlapping restriction fragments of the complete mitochondrial DNA (mtDNA) genome resulted in simple Y 2D gel patterns. Large single-stranded DNA molecules or double-stranded DNA molecules containing large or numerous single-stranded regions were found in the S. pombe mtDNA preparation. The replication of mtDNA monomers was found to occur in either direction. On the basis of these results, a replication mechanism for S. pombe mtDNA that is most consistent with a rolling circle model is suggested.

DNA Replication↗
PubMed1994

Negative and positive regulation of IGF-II mRNA expression in cultured rat cells by chicken serum.

We have investigated the possibility that some serum factors might negatively regulate the expression of the insulin-like growth factor-II (IGF-II) gene in 18-54, SF cells. Northern blot analyses indicated that there were three major transcripts (3.8 kb, 1.8 kb, and 1.2 kb) of the IGF-II gene in these cells. We found that incubation of 18-54, SF cells in medium containing very high concentrations (50-100%) of chicken serum greatly inhibited the steady-state level of all three IGF-II mRNA species. In addition, we also found that incubation of 18-54, SF cells in medium containing lower concentrations (10-50%) of chicken serum induced a 3.5 kb IGF-II mRNA. The inhibitory effect of high concentrations of chicken serum on IGF-II mRNA expression was not due to a cytotoxic effect of the serum, because these cells were maintained in 100% chicken serum for up to two weeks without loss of cell viability. The inhibitory effect of chicken serum on IGF-II mRNA was reversible after withdrawal of the serum. Nuclear run-on assays suggested that this negative regulation of IGF-II mRNA in 18-54, SF cells by chicken serum was not the result of transcriptional inhibition. Treatment of 18-54, SF cells that had been previously incubated in 100% chicken serum for 24 h with actinomycin D resulted in a partial restoration of the expression of the 3.8 kb and 1.2 kb IGF-II mRNA in these cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Amanitins↗
PubMed1994

[Influence of thoracic spinal subarachnoid microinjection of phentolamine on the effect of electroacupuncture].

The influence of thoracic spinal subarachnoid microinjection of Phentolamine (Phen, 200ug/20ul) on the effect of electroacupuncture (EA) at Neiguan (PC 6) was observed in 42 urethan-chloralose anesthetized rabbits. Results showed that: 1) EA of Neiguan (PC 6) could significantly promote recovery of elevated ST-segments and T-waves of electrocardiogram induced by acute myocardial ischemia (AMI). 2) subarachnoid microinjection of phentolamine had no marked influence on recovery of ST-segments and T-waves, but impeded recovery of blood pressure of post-AMI; and 3) subarachnoid microinjection of phentolamine could significantly weaken or eliminate the effect of EA of Neiguan (PC 6) in accelerating recovery of ST-segments and T-waves of post-AMI. It denotes that alpha-receptors of intra-thoracic spinal cord participate in the action of EA of Neiguan (PC 6) in improving AMI, and the upper thoracic segment of the spinal cord is one of the links for connecting Neiguan and the heart.

Animals↗
PubMed1994

[Influence of electroacupuncture of neiguan (PC 6) on ami-induced changes in electrical activity of dorsal horn neurons].

The electrical activity of the dorsal horn (DH) neurons was recorded extracellularly by glass micro-pipettes in urethane-chloralose anesthetized rabbits to analyze the role of the thoracic segments (T2-T3) of the spinal cord in the integration of information from electroacupuncture (EA) at Neiguan (PC 6) and acute myocardial ischemia (AMI). Results were: 1) after AMI, of 83 DH neurons, 18 displayed a significant excitatory response, 14 an obvious inhibitory reaction and 51 no apparent change; 2) after EA at Neiguan (PC 6), of 10 neurons with AMI-induced excitatory response, the electrical activity of 9 neurons was suppressed and the other 1 still maintained its excitatory state; of 8 neurons with AMI-induced inhibitory response, 7 were relieved from the suppressed state, the other 1 had no change following EA; and 3) the receptive field and the responsive types to somatic stimulation were examined in 83 DH neurons. Results showed that signals from EA at Neiguan (PC 6) and AMI could converge to the DH neurons of T2-T3. It suggests that DH participates in the integrative course of information from EA and AMI and thus it is one of the connective links between Neiguan (PC 6) and the heart.

Acupuncture Points↗
PubMed1994

Guanosine induces necrosis of cultured aortic endothelial cells.

We have observed that treatment of cultured bovine aortic endothelial (BAE) cells with guanosine can inhibit the proliferation and viability of the cells. The addition of 500 mumol/L guanosine to the medium resulted in approximately 90% inhibition of cell proliferation. It also changed the morphology of BAE cells from having a small cobblestone-like appearance to a giant pancake-like morphology. At a concentration range of 1 to 2.5 mmol/L, guanosine inhibited the viability of quiescent BAE cells. Incubation of the cells with 2 mmol/L guanosine for 24 hours maximally induced the loss of cell viability by approximately 80%. We also compared the effects of different nucleosides on the proliferation and viability of BAE cells and found that at appropriate concentration ranges, only guanosine was able to inhibit the proliferation and viability of the cells. To assess the mechanism that mediates the cytotoxicity of guanosine, we analyzed the degradation pattern of DNA in guanosine-treated cells and found that random DNA degradation occurred in the cells. Thus, we suggest that treatment of BAE cells with guanosine induced cell necrosis.

Animals↗
PubMed1994

[Anti-implantation action of nylestriol and its effect on endometrium in rabbits].

The anti-implantation action of nylestriol in rabbits was studied. Using the method of arresting mitosis by injection of colchicine, we detected the mitosis frequency of endometrial cells. The activities of carbonic anhydrase (CAH), A1P and PAS reaction were observed under light microscope combined with the histochemical method and microscopic autoexposure control device. The results were as follows: 1. Giving nylestriol orally to rabbits on day 1 of pregnancy produced an obvious anti-implantation effect; 2. The number of mitosis cells in glandular epithelium and stroma of the endometrium in the treatment group was less than that in the control group (P < 0.05); and 3. Compared with the control group, the activities of CAH and A1P, and glycogen content in the endometrium decreased significantly in the treatment group (P < 0.05). The result suggests that nylestriol may prevent the implantation of blastocyst by disturbing decidulization of the endometrium.

Alkaline Phosphatase↗
PubMed1993

Recombination walking: genetic selection of clones from pooled libraries of yeast artificial chromosomes by homologous recombination.

Recombination walking is based on the genetic selection of specific human clones from a yeast artificial chromosome (YAC) library by homologous recombination. The desired clone is selected from a pooled (unordered) YAC library, eliminating labor-intensive steps typically used in organizing and maintaining ordered YAC libraries. Recombination walking represents an efficient approach to library screening and is well suited for chromosome-walking approaches to the isolation of genes associated with common diseases.

Animals↗
PubMed1993

Differential orientations of the DNA-binding domain and carboxy-terminal dimerization interface regulate binding site selection by nuclear receptor heterodimers.

Retinoic acid, thyroid hormone, and vitamin D receptors preferentially activate target genes through response elements that consist of direct repeat arrangements of a core recognition motif of consensus sequence AGGTCA. We present evidence that the preference for direct repeat elements arises from two fundamental differences from steroid hormone receptors. First, retinoic acid, thyroid hormone, and vitamin D receptors are demonstrated to preferentially form heterodimers with the retinoid X receptors. These interactions are mediated by the carboxy-terminal dimerization interface, with heterodimer preference specified by actions of the DNA-binding domain. Second, the DNA-binding domains of heterodimeric receptors appear to be rotationally flexible with respect to the carboxy-terminal dimerization interface. Several independent lines of evidence suggest that, relative to the retinoid X and steroid hormone receptors, the DNA-binding domain of the thyroid hormone receptor is preferentially rotated by approximately 180 degrees with respect to its carboxy-terminal dimerization interface. As a result, solution interactions between the carboxy-terminal dimerization interfaces of the retinoid X and thyroid hormone receptors are predicted to lead to the preferential alignment of their respective DNA-binding domains in a direct repeat configuration. This alignment would position the retinoid X receptor over the upstream recognition motif of direct repeat response elements. Differential orientations of the DNA-binding domain, which contribute to the polarity of heterodimer binding, are regulated by a short sequence (the A box) that is located between the conserved DNA-binding and carboxy-terminal dimerization domains.

Amino Acid Sequence↗