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Biomedical subjects

L X Zhang

Publications and source records attributed to L X Zhang.

At least 19 recordsLinked to original sources
PubMed1992

Carotenoids up-regulate connexin43 gene expression independent of their provitamin A or antioxidant properties.

Epidemiological evidence and studies in whole animals and cell culture have indicated that carotenoids have cancer chemopreventive action. In mouse C3H10T1/2 cells, this activity is highly correlated with the ability of carotenoids to up-regulate gap junctional intercellular communication. Here, we report that in mouse cells, carotenoids increase the expression of connexin43, a gene that encodes a major gap junction protein. This effect appears unrelated to their provitamin A or antioxidant properties, since carotenoids with and without provitamin A activity increased levels of connexin43 mRNA and protein, whereas the antioxidants methyl-bixin and alpha-tocopherol were inactive. Moreover, the active carotenoid canthaxanthin did not induce the vitamin A-inducible gene retinoic acid receptor-beta. Connexin43 is the first carotenoid-inducible gene described in mammals. By indicating an additional pathway through which carotenoids function, these data provide a mechanistic basis for cancer chemoprevention by carotenoids and may lead to a re-evaluation of carotenoid physiology.

Animals↗
PubMed1992

Tuberculosis control programme in Beijing.

Since 1978 a new tuberculosis control programme based on modern concepts has been started in Beijing. The main goals of the programme were: (1) To prioritize the control of sources of infection; (2) to instigate fully supervised treatment (FST) for new smear-positive patients; (3) to extend services to the rural areas. A four-level network of tuberculosis control services has been organized both in urban and rural areas. Tuberculosis control has been integrated into rural primary health care. Coverage of FST among new smear-positive cases increased to 93% in 1990. A standard regimen, 1HS/11H2S2 has been used for initial treatment. A reserve regimen of RFP and EMB was added to those who failed to convert in 6 months. Since 1988 a 6-month intermittent short-course regimen has been introduced as standard regimen. Case-finding has been intensified since 1980 through symptomatics. Control of chronic excreters was achieved through FST of new smear-positive cases and fully supervised retreatment of old chronic cases. The new tuberculosis control programme has proved highly successful in controlling sources of infection. The prevalence of smear-positive pulmonary tuberculosis in Beijing during the national surveys in 1979, 1984-1985 and 1990 was 127, 56 and 16 per 100,000 respectively. The average annual reduction rate was 17%. This successful experiment has been recognized as a model for the whole country.

Antitubercular Agents↗
PubMed1992

Inhibition of cellular transformation by triphenylmethane: a novel chemopreventive agent.

Triphenylmethane (TPM) was found to inhibit 3-methyl-cholanthrene-induced neoplastic transformation of 10T1/2 cells in a dose-dependent manner (ED50 = 2.8 microM). This activity was independent of any effect on intercellular communication and did not appear to be directly related to the general antioxidant properties of TPM as measured by cellular thiobarbituric acid-reactive substances. Triphenylmethanol (TPMOL) and diphenylmethane also inhibited transformation (ED50 = 6.9 and 90 microM respectively). TPM had no effect on the proliferation of exponentially growing cells. At higher concentrations TPM and its analogues enhanced plating efficiency of cells indicating no significant toxicity for these compounds at levels up to 50 microM. The inhibitory effects of TPM on transformation were reversible when TPM was removed from the medium. While TPM had no effect on the growth of fully transformed cell lines, it was able to inhibit the growth of 1/3 neoplastic foci in the presence (but not absence) of 10T1/2 cells. TPM was found to stimulate protein kinase C (PKC) activity for both crude C3H10T1/2 cytosolic PKC and purified PKC obtained from rat brain. The ability of TPM to stimulate PKC activity appeared to be dependent on [CaCl2] and the order of reagent addition in the assay. Tamoxifen, a structurally related compound to TPM, was also found to enhance PKC activity over the same concentration range but was less potent than TPM. The biological effects of TPM and related compounds indicate that they function in a manner distinct from other highly unsaturated transformation inhibitors such as carotenoids and retinoids. The inability of triphenylene to inhibit transformation suggests that a reactive methyl carbon may be essential for activity.

Animals↗
PubMed1992

Suppression of audiogenic epileptic seizures by intracerebral injection of a CCK gene vector.

P77PMC rat is a breed of rat with congenital audiogenic seizure (AS). AS attacks could be suppressed by cholecystokinin octapeptide (CCK-8) injected intracerebroventricularly (i.c.v.). In the present study we made i.c.v. injection of plasmid pSV2-beta Gal or pSV2-CCK encapsulated with lipofectin. Expression of pSV2-beta Gal in brain occurred from d 1 to d 14, with maximal expression at d 3 and d 4. After i.c.v. injection of pSV2-CCK plasmid, the AS of the P77PMC rats was markedly reduced, which was most obvious at d 3 and d 4. The time course of the AS repression was almost identical with that of pSV2-beta Gal expression. The results suggest that the repression of the AS in P77PMC rats is accounted for by the expression of foreign CCK gene in brain tissue.

Acoustic Stimulation↗
PubMed1991

Carotenoids enhance gap junctional communication and inhibit lipid peroxidation in C3H/10T1/2 cells: relationship to their cancer chemopreventive action.

We have previously demonstrated that diverse carotenoids inhibit chemically induced neoplastic transformation in 10T1/2 cells. To address their mechanism of action, the effects of six diverse carotenoids, with or without provitamin A activity, on gap junctional communication and lipid peroxidation have been investigated. beta-Carotene, canthaxanthin, lutein, lycopene and alpha-carotene increased gap junctional intercellular communication in a dose-dependent manner in the above order of potency, whereas m-bixin was inactive at concentrations up to 10(-5) M. alpha-Tocopherol, a potent chain-breaking antioxidant, caused a marginal enhancement of junctional communication. The enhancement of junctional communication by diverse carotenoids showed a strong statistical correlation with their previously determined ability to inhibit methylcholanthrene-induced neoplastic transformation (r = -0.75). All carotenoids tested inhibited lipid peroxidation, but with differing potencies. alpha-Tocopherol was the most active inhibitor followed by m-bixin. The capacity of carotenoids or alpha-tocopherol to inhibit lipid peroxidation was neither consistent with their ability to inhibit neoplastic transformation (r = 0.30) nor to increase junctional communication (r = 0.12). Since junctional communication appears to play an important role in cell growth control and carcinogenesis, we propose that in this system carotenoid-enhanced intercellular communication provides a mechanistic basis for the cancer chemopreventive action of carotenoids. These data also imply that carotenoids function in a manner analogous to retinoids in the 10T1/2 assay system. Interestingly this activity appears independent of their provitamin A status.

Animals↗
PubMed1991

[Inhibitory effect of tripterine on activities of IL-1, IL-2 and release of PGE2].

Tripterine is one of the components isolated from Tripterygium wilfordii Hook. Previous studies demonstrated that tripterine inhibited not only humoral and cellular immune responses but also some inflammatory responses. The present investigation attempted to observe effect of the drug on productions of IL-1 from macrophages, IL-2 from splenocytes and PGE2 from synovial cells. The results showed that tripterine (0.1-1.0 microgram/ml) significantly inhibited IL-1 activity of murine peritoneal macrophages induced by LPS. Because both intracellular and extracellular IL-1 activities were decreased, so tripterine might be able to reduce the production and release of IL-1. Besides, inhibition of IL-1 production was observed when macrophages were pretreated with the drug for 8 h and 16 h. A good relationship was found between the effect and concentration of tripterine which inhibited IL-2 production from ConA-activated murine splenocytes. Kinetic study indicated that IL-2 production was decreased when splenocytes were pretreated with the drug for 3 h, 6 h and 12 h. Synovial cells obtained from rabbit knee joint were cultured successfully. A23187 was found to augment PGE2 synthesis modestly. Tripterine significantly reduced PGE2 release from synovial cells in a concentration dependent manner.

Animals↗
PubMed1991

[Studies on RESA in Plasmodium falciparum culture medium].

P. falciparum grown in the complete RPMI 1640 medium (containing about 10% normal rabbit serum) for 24 h was collected at about 5% parasitemia. The medium was centrifuged at 500g for 20 min and the supernatant was then centrifuged once more at 40,000g for 30 min. Ten serum samples from falciparum malaria patients with anti-RESA antibodies collected from Yunnan Province were mixed with different dilutions of the culture supernatant, incubated at 37 degrees C for 2h and then at 4 degrees C overnight, and used for conducting RESA-IFA test. The titers of RESA-IFA test of all samples were reduced as compared with controls. When heated supernatant was used in the test, the inhibitory activity remained unchanged. The results indicate that RESA in the supernatants was soluble and heat-stable. To establish the origin of the reacting antigens in the inhibition experiments, the soluble fraction of sonicated merozoite-enriched collection and sonicates of ghost made from normal O phenotype erythrocytes were used in the inhibition RESA-IFA test with sera containing anti-RESA antibodies. The results showed that merozoite-enriched preparations were fully inhibitory at the concentration of 3.1 micrograms/ml, while no inhibition was observed at 0.2 micrograms/ml. In contrast, similar extracts made from normal erythrocyte ghosts were not inhibitory until concentrations about 30 times higher than that of merozoite antigen.

Adolescent↗
PubMed1990

[Immunosuppressive and antiinflammatory activities of tripterine].

Tripterine is one of the active components isolated from Tripterygium wilfordii Hook.f. In this study tripterine was shown to inhibit the antibody response of mouse splenocytes to SRBC both in vitro and in vivo either by primary or secondary stimulation. Tripterine was also found to significantly inhibit cotton pellet induced granuloma growth in rats and depress the delayed hypersensitive reaction of mouse skin to dinitrochlorobenzene (DNCB). Besides, it also increased the sleeping time of mouse induced by pentobarbital sodium. From the results stated above, it appears that tripterine might be useful in the treatment of inflammatory diseases or autoimmune diseases.

Animals↗
PubMed1989

The control of chronic infectious patients with pulmonary tuberculosis in a rural area of China.

The aim of this study was to reduce the prevalence of chronic infectious cases (CIC) in a rural area of China by fully supervised chemotherapy of newly diagnosed smear-positive cases and by reducing the number of existing old CIC through fully supervised retreatment. From 1980 to 1985, 83.3% of 1828 new, smear-positive cases were given fully supervised chemotherapy. In 1980, 95.2% of 565 old CIC started fully supervised retreatment. The prevalence of CIC had dropped from 40.5/100,000 in 1980 to 6.7/100,000 by the end of 1986.

Antitubercular Agents↗
PubMed1989

[Determination of the contents of mineral elements in the soil where the jinin big-wild ginseng grows].

The element contents in the soil where the Jilin Big-Wild Ginseng grows were determined with plasma emission spectrometry. 23 elements in the soil were found, of which 12 are macro and trace elements indispensable to Ginseng growth. This study provides a scientific basis for selecting suitable soil for planting wild ginseng, or for creating optimum soil conditions for the bumper harvest and high quality of Ginseng.

Calcium↗
PubMed1989

Dot-immunobinding assay (DIBA) with integral Plasmodium falciparum as antigen in immuno-diagnosis of falciparum malaria.

Among the available immuno-diagnostic methods of parasitoses, dot-immunobinding assay (DIBA) has been proved to be promising for its high sensitivity and specificity, easy performance, lack of need of special equipment, and consequently its practical usage in field work. In previously reported tests, soluble antigen was used, thus a sonicator and an ultracentrifuge were required to produce the antigen. This paper reports the application of integral P. falciparum as antigen in DIBA to detect antibodies in falciparum malaria cases. Of 52 sera from falciparum malaria patients tested, 49 (94.2%) showed positive reactions, which was similar to the result using soluble antigen in DIBA (96.2%) and was higher than that in IFA (86.5%) and ELISA (80.8%). No false positive was revealed in 48 control sera from healthy individuals and sera from visceral leishmaniasis, paragonimiasis, fasciolopsiasis and schistosomiasis patients.

Animals↗
PubMed1987

The primary structure of the lactate dehydrogenase isozyme M4 from giant panda.

The amino acid sequences of tryptic, chymotryptic and cyanogen bromide cleavage peptides of the lactate dehydrogenase isozyme M4 from giant panda have been determined. Based on the overlapping peptides and by a comparison with the known sequence of porcine lactate dehydrogenase isozyme M subunit, the complete primary structure of the giant panda lactate dehydrogenase isozyme M subunit has been established. The polypeptide chain of giant panda lactate dehydrogenase isozyme M subunit consists of 331 amino acid residues. There is a variance of 17 amino acid residues between the porcine and the giant panda lactate dehydrogenase isozyme M subunits. Most of the variable residues are substitutions by chemically similar amino acids and take place at residues not related to the active center of the enzyme.

Amino Acid Sequence↗
PubMed1987

A comparison of the primary structures of lactate dehydrogenase isozymes M4 from giant panda, red panda, black bear and dog.

Lactate dehydrogenase isozymes M4 have been isolated and purified from red panda (Ailurus fulgens), black bear (Selenarctos thibetanus) and dog (Canis familiars) by affinity chromatography and compared with that from giant panda (Ailuropoda melanoleuca). Experimental results have shown that the N-termini, C-termini and the molecular weights of LDH-M subunits of red panda, black bear and dog are the same as those of the LDH-M subunit of giant panda. Analysis and comparison of HPLC peptide maps from the tryptic digests of the isozymes of red panda, black bear and dog have shown that most of their peptide fragments had the same retention time and amino acid composition as the corresponding peptide fragments from giant panda. Fragments with different retention times and/or amino acid compositions were sequenced. Careful examination of those variant amino acid residues demonstrated clearly that the primary structure of giant panda LDH-M subunit is unique and it appears that the giant panda might be classified as an independent family.

Amino Acid Sequence↗