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Biomedical subjects

X Xiang

Publications and source records attributed to X Xiang.

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

Nuclear migration, nucleokinesis and lissencephaly.

During the past 20 years, biologists have become used to finding that proteins first identified in simple, genetically manipulable eukaryotic organisms are conserved in higher eukaryotes. This article draws attention to the similarity between NUDF protein, which is required for nuclear migration in the filamentous fungus Aspergillus nidulans, and a mammalian homologue, LIS1, whose malfunction causes lissencephaly, a neuronal migration disease. The authors suggest that there might be an underlying similarity of mechanism between nuclear migration in the fungus and neuronal migration in the brain.

Animals↗
PubMed1998

Extended-spectrum beta-lactamase-producing Klebsiella pneumoniae strains causing nosocomial outbreaks of infection in the United Kingdom.

Representative isolates from 10 distinct extended-spectrum beta-lactamase-producing strains of Klebsiella pneumoniae that caused hospital outbreaks in the United Kingdom from 1991 to 1994 were examined for relationships between their enzymes and plasmids. The beta-lactamases were identified by a combination of isoelectric focusing and gene sequencing. SHV-2 beta-lactamase was produced by isolates from four outbreaks, SHV-5 was involved in three, and SHV-4, TEM-15, and TEM-26 were involved in one outbreak each. All of the extended-spectrum beta-lactamases were encoded by self-transmissible plasmids, with sizes ranging from about 70 to 160 kb. No similarities between the restriction digest patterns of the extended-spectrum beta-lactamase-encoding plasmids were detected, except to some extent between those that produced TEM-15 and TEM-26. Thus, outbreaks of hospital infection with these organisms in the United Kingdom from 1991 to 1994 involved distinct organisms and resistance plasmids and appeared to be unrelated.

Aminoglycosides↗
PubMed1998

[Detection of Toxoplasma gondii DNA in the autopsy cases of abnormal birth and teratosis by polymerase chain reaction].

Toxoplasma gondii DNA in the autopsy tissues of 72 cases of the premature, stillbirth and congenital malformation was detected using polymerase chain reaction (PCR). The specific amplified products were found in 9 cases, i.e. one case of premature, 3 cases of stillbirth, one case of hydrocephalus and 4 cases of other teratosis. The positive rate was 12.5%. Ten control samples were negative. The results showed that Toxoplasma gondii infection was present in the disease cases. The finding indicates that the infection of Toxoplasma gondii may be one of the main causes of the abnormal birth and the congenital teratosis.

Animals↗
PubMed1998

[Ultrastructural pathologic research on the adult laryngeal papilloma].

In this paper, the ultrastructural features of laryngeal papillomas of 9 cases of adult patients were investigated by means of SEM. It showed that the polypoid surface of the papilloma is easily recognized; the surface cells are covered by microvilli of different size and shape; and the epithelium is bordered by an irregular and continuous basement membrane. In some areas, there is pseudopodium of basal cells stretching into connective tissue. The structure of interface between basement membrane and connective tissue varies with aggravation of tumor cell atypia. The significant variation of structural of basement membrane and semidesmosomes suggests the possibility of malignant change.

Aged↗
PubMed1998

[Establishment of Hymenolepis diminuta-animal model and morphology of cysticercoid].

AIM: To observe the morphological changes in the process of the development of Hymenolepis diminuta. METHODS: The life cycle of Hymenolepis diminuta was established between Rattus domesticus albus and Triboliun castaneum. The morphology of cysticercoid were observed microscopically, and the ultrastructure of the body surface of cysticercoid were observed by scanning electron microscopy. RESULTS: Three phases including the mature stage, the blister stage and the protective outer membrane-forming stage during the growing course of cysticercoid were observed microscopically. Under scanning electron microscope, lots of sieve-like micropores on the surface of mature cysticercoid were seen in the second week after infection. The blister phase was found in the third week and the outer membrane measuring about 45 microns in thickness were found surrounding the cysticercoid and vesicular surface, forming a smooth cyst wall in the fourth week. CONCLUSION: The life cycle of Hymenolepis diminuta has been established in the animal-model. The finding of the three phases during the growing course of cysticercoid is reported for the first time.

Animals↗
PubMed1997

Mutations in the heavy chain of cytoplasmic dynein suppress the nudF nuclear migration mutation of Aspergillus nidulans.

To identify proteins that interact directly or indirectly with the NUDF protein, which is required for nuclear migration in Aspergillus nidulans, we initiated a screen for extragenic suppressors of the heat-sensitive nudF6 mutation. Suppressor mutations in at least five genes, designated snfA-snfE, caused improved growth and nuclear migration at high temperatures compared to the nudF6 parent. Two snfC mutations mapped near the nudA gene, which encodes the cytoplasmic dyncin heavy chain, and could be repaired by transformation with wild-type nudA DNA, demonstrating that they are mutations in nudA. The snfC mutations are bypass suppressors of nudF and genetic evidence indicated that NUDA and NUDF act in the same nuclear migration pathway. Taken together, our data suggests that NUDF affects nuclear migration by acting on the dynein motor system.

Aspergillus nidulans↗
PubMed1997

Association analysis of the dopamine D4 gene exon III VNTR and heroin abuse in Chinese subjects.

Although social and cultural influences are clearly important, family, twin and adoption studies indicate that genes contribute significantly to substance abuse. Substance abuse is associated with novelty seeking, a heritable human personality trait which may be influenced by alleles of the dopamine D4 (DRD4) gene exon III VNTR. Consequently Kotler et al analysed the DRD4 VNTR in opiate-dependent subjects from Israel, and found a significant excess of the 7-repeat allele. We have attempted to replicate this finding using a Han Chinese case-control sample of 121 heroin-dependent subjects and 154 normal controls. We found two 7-repeat alleles which occurred exclusively in the patient group, and overall there was an excess of longer alleles, which did not reach significance (chi 2 = 7.04; P = 0.07). When the D4 VNTR was divided into 'long' (5-7 repeats) and 'short' (2-4 repeats), a significant excess of long alleles was observed in the patient group (P = 0.023, one-tailed), with an odds ratio of 2.30 (95% CI 1.07-4.93). We conclude that our findings support the hypothesis that alleles of the DRD4 exon III VNTR are susceptibility factors for heroin abuse.

Adolescent↗
PubMed1997

Deletion of nudC, a nuclear migration gene of Aspergillus nidulans, causes morphological and cell wall abnormalities and is lethal.

Nuclear migration is required for normal development in both higher and lower eukaryotes. In fungi this process is mediated by cytoplasmic dynein. It is believed that this motor protein is anchored to the cell membrane and moves nuclei by capturing and pulling on spindle pole body microtubules. To date, four genes have been identified and shown to be required for this process in Aspergillus nidulans. The nudA and nudG genes, respectively, encode the heavy and light chains of cytoplasmic dynein, and the nudF and nudC gene products encode proteins of 49 and 22 kDa. The precise biochemical functions of the nudF and nudC genes have not yet been identified. In this report we further investigate NUDC protein function by deleting the nudC gene. Surprisingly, although deletion of nudA and nudF affect nuclear migration, deletion of nudC profoundly affected the morphology and composition of the cell wall. Spores of the strain deleted for nudC grew spherically and lysed. The thickness of the cell wall was increased in the deletion mutant and wall polymer composition was abnormal. This phenotype could be repressed by growth on osmotically buffered medium at low temperature. Similar, but less severe, effects were also noted in a strain depleted for NUDC by down-regulation. These results suggest a possible relationship between fungal cell wall biosynthesis and nuclear migration.

Actins↗
PubMed1997

Mechanism and stability of hyperproduction of the extended-spectrum beta-lactamase SHV-5 in Klebsiella pneumoniae.

Some isolates of SHV-5 beta-lactamase-producing Klebsiella pneumoniae K2 from a single-strain outbreak of cross-infection produced approximately five-fold more beta-lactamase than others. We investigated three possible genetic mechanisms of this hyperproduction: the presence of a more powerful promoter, an increase in plasmid copy number or an amplification of the gene on a plasmid. No differences between low and high beta-lactamase producers were detected in the promoter region of the SHV-5 beta-lactamase gene, which closely resembled that of SHV-2. SHV-5 beta-lactamase production was encoded on a low copy number plasmid, but DNA-DNA hybridization with an SHV-specific probe detected a higher gene dose in hyperproducers. The beta-lactamase hyperproduction was unstable on repeated subculture, with a reduction of about 75% after 100 generations. Hyperproducing mutants of a low-producing Klebsiella and its Escherichia coli K-12 transconjugants could be selected in vitro at a frequency of 10(-5) to 10(-6) and these variants had an increased SHV-5 beta-lactamase gene copy number on low copy number plasmids. We conclude that hyperproduction of the extended-spectrum beta-lactamase was caused by gene amplification that could be easily lost or gained in vitro. Since the change to hyperproduction occurred at a high frequency and hyperproducers showed increased resistance to many beta-lactams and beta-lactam/beta-lactamase inhibitor combinations, we suspect that these variants may readily be selected in patients during antibiotic therapy.

DNA, Bacterial↗
PubMed1997

A prolactin-inducible T cell gene product is structurally similar to the Aspergillus nidulans nuclear movement protein NUDC.

Clone 15 (c15) was originally identified as a PRL-inducible gene in activated T cells. Sequence analysis of c15 revealed that the last 94 amino acids of c15 are 68% identical and 78% similar to the filamentous fungus Aspergillus nidulans nuclear movement protein NUDC. The identification of the mammalian (rat) c15 protein suggests that the carboxy-terminal NUDC-like region has been conserved over evolution for an important structure and/or function. To determine whether c15 is functionally analogous to NUDC, complementation studies were performed using the inducible/repressible pAL5 vector system. The results of the complementation experiments show that the full-length mammalian c15 protein is not only capable of rescuing the nuclear movement defect of the nudC3 mutants, but is also able to restore the expression of the downstream endogenous NUDF protein to near wild type levels. These results indicate that rat c15 and fungal NUDC not only share similar structures, but also serve similar functions. Taken together, the structural and functional conservation between c15 and NUDC is consistent with the notion that c15 is the rat homolog of nudC and has therefore been given the name RnudC.

Animals↗
PubMed1997

Neoplastic transformation and cytogenetic aberrations of rat tracheal epithelial cells induced by alpha-particle irradiation.

Primary rat tracheal epithelium (RTE) cells can be transformed in vitro by alpha-particles irradiation. One out of 3 isolated morphologically transformed colonies gave rise to an immortal cell line and ultimately became neoplastic by successive passaging. Cytogenetic analysis was performed on the cell line in order to understand how the specific chromosome alterations participate in the process of neoplastic transformation of RTE cells. The 5th, 18th, 39th passage cells and the colony cells isolated from soft agar (SA) culturing of the 40th passage cells were analyzed. The results showed that the 20th passage cells were nontumorigenic, but the 40th passage cells were tumorigenic. The increase of the length of the long arm of chromosome 15 (15q+) was frequent at the 5th passage (67.8%), especially in SA cells in which it occurred in a clonal fashion (100%). Therefore, 15q+ might be the critical gene lesion after alpha-particles irradiation. Monosomy of chromosome 8 that occurred frequently at passage 5 (54%) and 40 (53%) might be correlated with earlier transformation of RTE cells. In addition, three marker chromosomes (M1, M2 and M3) showed a passage-dependent increase. In particular M1 and M2 that were highly frequent at passage 39 (90%) suggested that they might play an important role in the process of cell transformation.

Alpha Particles↗
PubMed1997

[Preliminary application of PCR to curative effect assessment of chemotherapy against experimental acute infection of Toxoplasma gondii in mice].

Treatment with pyrimethamine and sulfamethoxazolum combination administered via intragastric route, was started 2 hours after each mouse received an intraperitoneal injection of a lethal inoculum of 5 x 10(3) tachyzoites of RH strain toxoplasma gondii and the therapy was lasted for 52 days. Combined therapy of the two drugs resulted in 83.3% survival rate in mice. PCR and the conventional mouse inoculation (MI) were compared for their validity as an curative effect assessing method. The positive rates of PCR and MI were 63.64% and 18.18%, respectively. The results suggest that PCR can be used in studies involving drug screening and curative effect assessment of anti-Toxoplasma chemotherapy in vivo. In addition, the results indicated that longer course of treatment against toxoplasmosis is required in clinical practice.

Animals↗
PubMed1997

[Effects of inhalated isosorbide dinitrate on endothelin and nitric oxide and its therapeutic efficacy for experimental guinea-pigs with asthma].

To probe into the correlation between the changes of endothelin and nitric oxide in bronchial alveolar lavage fluid (BALF) and the treatment of inhaling isosorbide dinitrate on experimental guinea pigs with asthma, we divided 25 guinea pigs randomly into three groups (Control group, Asthma group, Isosorbide dinitrate group), and induced some subjects by inhalation of aerosolized ovalbumin as the model of asthma to investigate the endothelin (ET) and nitric oxide (NO) level in BALF as well as the pathological change of the respiratory tract. We found that the level of endothelin and nitric oxide in BALF were all elevated in experimental guinea pigs with asthma, but the degree of increase of NO in BALF was lower than that of ET. The NO and the ET levels in BALF were negative correlation (r = -0.8050, P < 0.01). After having been treated with aerosolized isosorbide dinitrate, the NO level in BALF was significantly elevated and the ET level in BALF was decreased in comparison with the asthma group (P < 0.001, respectively). Moreover, the eosinophile infiltration, exoserosis, and epithalaxia of the respiratory tract of the guinea-pigs were all lightened. The results suggest that inhaled isosoratory dinitrate could be used for treating asthma, and its mechanism may be elevation of NO level and decrease of ET level in BALF.

Administration, Inhalation↗
PubMed1996

Mapping 638 STSs to regions of human chromosome 3.

The initial step of mapping STSs to chromosome 3 has been by mapping to a reference panel of 21 somatic cell hybrids containing fragments of chromosome 3. In this study we map 638 STSs to 23 bins on chromosome 3. The bin information greatly facilitates further mapping by radiation hybrids and YAC clones.

Chromosome Mapping↗
PubMed1996

[Obstetric quality investigation on urban and rural area in China].

OBJECTIVE: A survey on implementing the proclamation in "National plan of action for the survival, protection and development of children in 1990s" in China (NPA), by reducing the maternal mortality rate (MMR) by half and the infant mortality rate (IMR) by 1/3 by the year 2000 as a proof of improved obstetric quality. METHOD: The maternal and child health (MCH) bureau, ministry of health, have called on a cooperative investigation on obstetric quality in 75 obstetric clinics in 11 provinces, municipalities or autonomous regions, randomly sampled from each of the 6 governmental areas in China. The data were collected and analyzed centrally, together with the yearly reports from the monitored county hospitals. RESULTS: Senior medical professionals associated to 32.68% in provincial and teaching hospitals while only 2.63% in the country hospitals. The former are provided with all necessary equipment while the latter with inadequate and outdated ones. MMR declined year by year, more marked wherever hospital delivery rate was high and when the numbers of antenatal visit were more. However, when antenatal visit began late in pregnancy, MMR rose Zhejiang province and Shanghai ranked first in obstetric quality because of an efficient systematic management of the pregnancies. CONCLUSIONS: Having enough leading professionals in this specialty to train adequate medical ground personnel at grass root level; providing sufficient medical installations; enforcing easily and good quality antenatal care and increasing hospital deliveries carried out under authoritative management are important points to raise the quality of obstetrics.

China↗
PubMed1995

Characterization and localization of the cytoplasmic dynein heavy chain in Aspergillus nidulans.

Migration of nuclei throughout the mycelium is essential for the growth and differentiation of filamentous fungi. In Aspergillus nidulans, the nudA gene, which is involved in nuclear migration, encodes a cytoplasmic dynein heavy chain. In this paper we use antibodies to characterize the Aspergillus cytoplasmic dynein heavy chain (ACDHC) and to show that the ACDHC is concentrated at the growing tip of the fungal mycelium. We demonstrate that four temperature-sensitive mutations in the nudA gene result in a striking decrease in ACDHC protein. Cytoplasmic dynein has been implicated in nuclear division in animal cells. Because the temperature-sensitive nudA mutants are able to grow slowly with occasional nuclei found in the mycelium and are able to undergo nuclear division, we have created a deletion/disruption nudA mutation and a tightly downregulated nudA mutation. These mutants exhibit a phenotype very similar to that of the temperature-sensitive nudA mutants with respect to growth, nuclear distribution, and nuclear division. This suggests that there are redundant backup motor proteins for both nuclear migration and nuclear division.

Antibodies, Fungal↗
PubMed1995

Nuclear migration advances in fungi.

Nuclear migration encompasses three areas: separation of daughter nuclei during mitosis, congress of parental nuclei before they fuse during fertilization, and positioning of nuclei in interphase cells. This review deals primarily with interphase nuclear migration, which is crucial for events as disparate as vertebrate embryonic development and growth of fungal mycelia. Mutants of Aspergillus nidulans, Neurospora crassa and Saccharomyces cerevisiae have been particularly informative, and a detailed molecular analysis of this process is now well under way.

Journal Article↗