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Biomedical subjects

D Yang

Publications and source records attributed to D Yang.

At least 415 records · Page 23Linked to original sources
PubMed1993

Ultrasonic monitoring during replacement of frozen/thawed embryos in natural and hormone replacement cycles.

We evaluated the results of cryopreserved/thawed embryo replacement (FER) to determine if the outcome following transfer in a natural cycle in a defined group was different to that from a hormone replacement cycle, and also to assess vaginal ultrasonographic features that assist in predicting the timing of the transfer. At the London Fertility Centre, 149 consecutive FER cycles were studied retrospectively. Women with proven ovulation and regular cycles were included during natural cycles (n = 77). The hormone replacement cycle group included women with anovulation, irregular cycles and older women (n = 72). In the natural cycle group, transfer was performed following positive urinary luteinizing hormone (LH) surge and confirmation of ovulation by ultrasonography. With the hormone replacement therapy group, gonadotrophin-releasing hormone analogue was used to induce pituitary down-regulation, oestradiol valerate was supplemented followed by regular ultrasound monitoring, and FER 2 days following the initiation of progesterone, which was started once adequate endometrial development was noticed on ultrasonography. The pregnancy and ongoing/delivery rates were analysed in relation to the treatment cycle, age, number and quality of embryos transferred. Ultrasonographic features were examined to evaluate their relationship with the outcome of treatment. The results showed that no difference existed between natural and hormone replacement cycles in pregnancy rates per cycle (26 and 25%), ongoing/delivery rate (20.8% in both groups), and implantation rate (10.3 and 10.6%). Pregnancy rates were not influenced by the number of embryos transferred, stage at which the embryos were cryopreserved, or whether they were extra embryos from in-vitro fertilization/embryo transfer, or gamete intra-Fallopian transfer.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Clostridium ljungdahlii sp. nov., an acetogenic species in clostridial rRNA homology group I.

Clostridium ljungdahlii sp. nov. strain ATCC 49587T (T = type strain) was isolated from chicken yard waste for its ability to produce ethanol from synthesis gas. This gram-positive, motile, sporeforming rod's metabolism was primarily acetogenic. C. ljungdahlii grew with carbon monoxide, hydrogen and carbon dioxide, ethanol, pyruvate, arabinose, xylose, fructose, or glucose. Methanol, ferulic acid, lactate, galactose, and mannose did not support growth. The G+C content was 22 to 23 mol%. C. ljungdahlii is the first acetogen in clostridial 23S rRNA homology group I.

Animals↗
PubMed1993

Assignment of fatty acid-beta-oxidizing syntrophic bacteria to Syntrophomonadaceae fam. nov. on the basis of 16S rRNA sequence analyses.

After enrichment from Chinese rural anaerobic digestor sludge, anaerobic, sporing and nonsporing, saturated fatty acid-beta-oxidizing syntrophic bacteria were isolated as cocultures with H2- and formate-utilizing Methanospirillum hungatei or Desulfovibrio sp. strain G-11. The syntrophs degraded C4 to C8 saturated fatty acids, including isobutyrate and 2-methylbutyrate. They were adapted to grow on crotonate and were isolated as pure cultures. The crotonate-grown pure cultures alone did not grow on butyrate in either the presence or the absence of some common electron acceptors. However, when they were reconstituted with M. hungatei, growth on butyrate again occurred. In contrast, crotonate-grown Clostridium kluyveri and Clostridium sticklandii, as well as Clostridium sporogenes, failed to grow on butyrate when these organisms were cocultured with M. hungatei. The crotonate-grown pure subcultures of the syntrophs described above were subjected to 16S rRNA sequence analysis. Several previously documented fatty acid-beta-oxidizing syntrophs grown in pure cultures with crotonate were also subjected to comparative sequence analyses. The sequence analyses revealed that the new sporing and nonsporing isolates and other syntrophs that we sequenced, which had either gram-negative or gram-positive cell wall ultrastructure, all belonged to the phylogenetically gram-positive phylum. They were not closely related to any of the previously known subdivisions in the gram-positive phylum with which they were compared, but were closely related to each other, forming a new subdivision in the phylum. We recommend that this group be designated Syntrophomonadaceae fam. nov.; a description is given.

Bacteria, Anaerobic↗
PubMed1993

Characterization of cell growth-inhibitory factor in inflammatory peritoneal exudate cells of rats.

We characterized the nature and reaction mode of the cell growth-inhibitory factor (here designated CGIF) from rat peritoneal exudate cells (PEC). The soluble fraction separated from the lysate of Enterococcus faecalis-induced 24 hr PEC completely inhibited Con A-induced thymocyte mitogenesis. Gel filtration chromatography showed that CGIF has a molecular weight of approximately 23-25 kDa. Isoelectric focusing with Rotofor indicates that the factor has an isoelectronic point of 5.8-6.4. CGIF was inactivated by treatment at 70 C, for 30 min or by tryptic digestion, but the activity was not destroyed by the reduction with dithiothreitol. As well as thymocyte proliferation, CGIF completely suppressed 3H-thymidine incorporation of splenocytes which were stimulated by either Con A or LPS, suggesting the factor is effective on both T and B cells. The acting point of the inhibitor appeared to be a later stage of the lymphocyte activation sequence, since it was still effective when added 28.5 hr after the addition of Con A. CGIF also reduced the viability of these cells when added with mitogens such as Con A or LPS. CGIF thus appears to be distinct from interleukin-1 receptor antagonist or transforming growth factor-beta.

Animals↗
PubMed1993

Heat stable interleukin-1 activity and activity inhibiting thymocyte proliferation in inflammatory polymorphonuclear leukocytes.

The present study demonstrates the co-existence of heat stable interleukin-1 (IL-1) and IL-1-suppressing activity in murine inflammatory polymorphonuclear leukocytes (PMNs). When the IL-1 activity in casein-induced PMN lysate was examined by lymphocyte activating factor assay, it peaked at a concentration of 2.5 x 10(6) cells per ml, but this activity was reduced to nothing at higher concentrations, suggesting the co-existence of IL-1 and IL-1-suppressive factors in PMNs. Although IL-1 has been reported to be inactivated by heat treatment, approximately one-fourth of the IL-1 activity was restored after treatment at 100 degrees C for 10 min. In gel chromatography, the IL-1 activity of the PMN-soluble fraction was eluted in two broad peaks with apparent molecular sizes of 17-23 kDa and 23-43 kDa, respectively. Since the heat stable IL-1 activity was mainly eluted in fractions corresponding to the latter peak, and was neutralized by IL-1 receptor antagonist (IL-1ra) or anti-IL-1 alpha antiserum, the heat stable IL-1 is suggested to be precursor form IL-1 alpha. A high concentration of soluble fraction from PMN lysate, in contrast, completely suppressed the activity of recombinant IL-1 alpha or beta, and the suppressive activity was heat labile. Since thymocyte mitogenesis by 5 micrograms/ml of concanavalin A (Con A) with or without IL-2 was also completely suppressed, the suppressive factor(s) may not be IL-1ra or transforming growth factor beta which were reported to be present in PMNs.

Animals↗
PubMed1993

Synthesis of [18F]fluoroalanine and [18F]fluorotamoxifen for imaging breast tumors.

To develop ligands for imaging breast tumors, [18F]fluoro analogue of tamoxifen and [18F]fluoroalanine were radiosynthesized. In vivo biodistribution studies were performed in mammary tumor-bearing rats. In studies on the biodistribution of an [18F]fluoro analogue of tamoxifen, tumor uptake decreased when rats were pretreated with diethylstilbestrol (DES), suggesting that tracer uptake in tumors was receptor-mediated. An estrogen receptor assay indicated that tumors have a receptor density of 7.5 fmol/mg protein. Studies of the distribution of [18F]fluoroalanine in tissue showed that the tumor-to-tissue ratio increases as a function of time. Positron emission tomography (PET) images of tumor-bearing rats demonstrated that tumors can be visualized 1 h after rats are injected with an [18F]fluoro analogue of tamoxifen. PET imaging of pigs after injection of 10 mCi of [18F]fluoro analogue of tamoxifen showed uterine uptake that could be blocked by DES (50 mg). The findings suggest that both radiotracers are useful for imaging breast tumors.

Alanine↗
PubMed1993

Hemodynamic effects of terazosin in congestive heart failure.

To determine the hemodynamic effects of a new alpha-1 blocker, terazosin, in congestive heart failure, 10 patients with this condition underwent hemodynamic testing at rest. Thirty minutes after the oral administration of 4 mg terazosin, mean right atrial pressure, mean pulmonary artery pressure and pulmonary capillary wedge pressure were found to be decreased, while the cardiac index was increased significantly. Improvement in hemodynamics persisted for more than 15 h, without an increase in heart rate. It is suggested that terazosin may have effective applications in the treatment of congestive heart failure.

Adolescent↗
PubMed1993

Immunological studies on the pathogenesis of pterygium.

Immunohistochemical, electron microscopic and routine pathological studies were conducted to observe the changes in T-cell subsets, B-cells, plasma cells, and mast cells, and the distributions of immunoglobulins (IgE, IgG, IgA, IgM) and C3 in patients with pterygium. The results were as follows. Massive amounts of infiltrating lymphocytes, predominantly T-cells (CD3+), were found in the substantia propria of the pterygial specimens. The helper-suppressor ratio had risen from 1:2.7 in the normal conjunctiva to 1:1.5. Positive cytoplasmic immunoglobulin staining indicated a plasmocytic infiltration in the lesions as well. Abnormal distributions of immunoglobulins were found, and deposition of immunoglobulins in a granular pattern around the basement membrane of the epithelial layer was seen. Mast cell reactions were found, and a linear correlation between the numbers of lymphocytes and mast cells was shown. Basement membrane destruction in the cap area of the pterygium was also confirmed. These results indicate that an immunologic mechanism, possibly of Types 1, 3 and 4 hypersensitivity, may contribute to the pathogenesis of pterygium.

Basement Membrane↗
PubMed1993

Immunological analysis of the zinc-binding peptides of surface metalloproteinase (gp63) of Leishmania major.

The surface metalloproteinase, gp63, is highly conserved and immunogenic. A peptide spanning the zinc-binding region of the molecule is immunogenic and can induce protective immunity in mice against Leishmania major infection. We report here that the minimum length of the immunogenic peptide in this region is a heptapeptide, VVTHEMA, corresponding to residues 161-167. Optimal immunogenicity is conferred by a decapeptide, LVTVVTHEMA, corresponding to residues 158 to 167, where H and E are consensus zinc-binding residues. These two residues determine the specificity of the peptide. The next two residues, M and A are necessary for the immunogenicity of the peptide. These results suggest that the zinc-binding residues are recognized by the T-cell receptor complex, while the two adjacent residues are involved in the peptide presentation by the major histocompatibility complex (MHC) molecule.

Amino Acid Sequence↗
PubMed1992

Reactivation of insulin-like growth factor II during hepatocarcinogenesis in transgenic mice suggests a role in malignant growth.

We have studied the expression of insulin-like growth factor II (IGF-II) during hepatocarcinogenesis in four independent transgenic mouse lines. In all four lines liver-directed transgene expression induces a stepwise and relatively synchronized tumorigenesis. IGF-II reexpression occurs in all four lines irrespective of the mechanism of tumor induction. Reexpression is chronologically associated with late progression steps toward hepatocellular carcinoma and correlated with the respective tumor progression rate in each line. IGF-II activation is focal and topographically associated with high replicative activity. IGF-II mRNAs in hepatocellular carcinomas show similarities to the expression pattern in fetal liver, and a M(r) 15,000 IGF-II polypeptide accumulates intracellularly in distinct cytoplasmic preferentially perinuclear compartments. These data indicate that IGF-II reexpression is a marker for progression to hepatocellular carcinoma and may contribute to hepatocarcinogenesis via an autocrine mechanism.

Animals↗
PubMed1992

Malignant transformation of human fibroblast cell strain MSU-1.1 by (+-)-7 beta,8 alpha-dihydroxy-9 alpha,10 alpha-epoxy-7,8,9,10-tetrahydrobenzo [a]pyrene.

Treatment of MSU-1.1 cells, a near-diploid, karyotypically stable, infinite life-span human fibroblast strain, with (+-)-7 beta,8 alpha-dihydroxy-9 alpha,10 alpha-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene induced focus formation. Eight independent foci were isolated and the cell strains developed from them were examined for characteristics of malignant cells. Each grew to a higher density in medium containing 1% serum than did the MSU-1.1 cells. Three of the eight grew rapidly in serum-free medium without added growth factors, formed colonies in agarose with diameters of greater than or equal to 120 microns at a frequency of 5-19%, exhibited loss of genetic material, and, when injected into athymic mice, formed sarcomas that reached 6 mm in diameter within 2-3 wk. One produced high-grade sarcomas (progressively growing, invasive tumors exhibiting high mitotic activity); the other two produced low-grade sarcomas (tumors with a lower degree of mitotic activity) that developed focal areas of high-grade malignant cells if left in the animals for greater than 4 wk. A fourth cell strain formed high-grade sarcomas only after 2.5-3 mo, but the tumor-derived cells analyzed showed the same growth properties as the three malignant cell strains described above, exhibited loss of genetic material, and, when reinjected into athymic mice, produced high-grade sarcomas with a short latency period.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗
PubMed1992

Effect of endothelin-1 on the uterine vasculature of the pregnant and estrogen-treated nonpregnant sheep.

OBJECTIVE: This study was designed to evaluate the uterine vascular responses to endothelin-1 in pregnant and estrogen-treated nonpregnant sheep. STUDY DESIGN: Seven pregnant and five nonpregnant oophorectomized ewes received local uterine artery infusions of endothelin-1, norepinephrine, and phenylephrine. Arterial blood pressure, heart rate, and uterine blood flow were recorded. RESULTS: Endothelin-1 (0.01 to 3.0 micrograms/min), norepinephrine (0.1 to 3 micrograms/min), and phenylephrine (0.1 to 10 micrograms) produced significant dose-related decreases in uterine blood flow and increases in uterine vascular resistance. On a nanomoles infused per minute basis, endothelin-1 was much more potent than norepinephrine and phenylephrine as a uterine artery vasoconstrictor in both pregnant and nonpregnant sheep. The uterine vascular responses to norepinephrine and phenylephrine were similar in pregnant and nonpregnant ewes, whereas response to endothelin-1 was blunted in pregnancy. CONCLUSION: Endothelin-1 is an extremely potent uterine vasoconstrictor in both pregnant and nonpregnant ewes, but the uterine vascular responsiveness to endothelin-1 is decreased in pregnancy.

Animals↗
PubMed1992

Effect of calcitonin gene-related peptide on the uterine vasculature of the nonpregnant ewe.

OBJECTIVES: The current study was designed to evaluate the uterine vascular effects of calcitonin gene-related peptide on the uterine vasculature of nonpregnant sheep and compare them with the effects of prostacyclin. STUDY DESIGN: Five nonpregnant oophorectomized ewes were instrumented with uterine and pulmonary artery flow probes and catheters. Dose-response curves were constructed according to increasing doses of calcitonin gene-related peptide (0.01, 0.03, 0.1, 0.3, 1, and 3, micrograms/min) and prostacyclin (0.03, 0.1, 0.3, 1, 3, and 10 micrograms/min) via 10-minute uterine artery infusions. RESULTS: Both calcitonin gene-related peptide and prostacyclin produced a significant increase in uterine blood flow and a decrease in uterine vascular resistance. Calcitonin gene-related peptide was found to be approximately 17 times more potent than prostacyclin as a vasodilator. Local uterine artery infusions of calcitonin gene-related peptide led to significant increases in heart rate but did not alter blood pressure, cardiac output, or total peripheral resistance at the doses tested. In contrast, at doses of prostacyclin that produced similar uterine vasodilatation, prostacyclin led to significant decreases in systemic arterial blood pressure and total peripheral resistance and increases in heart rate and cardiac output. CONCLUSION: These data strongly suggest that calcitonin gene-related peptide, an endogenously occurring vasoactive peptide, could play an important role in regulating uterine and systemic hemodynamics.

Animals↗
PubMed1992

Intra-hepatic-arterial infusion of misonidazole--an experimental study of regional radiosensitisation by intraarterial embolisation.

The purpose of this study was to generate a selective radiosensitising effect by the intra-hepatic-arterial infusion of misonidazole (MISO). MISO (10 mg) was infused after transcatheter hepatic-arterial embolisation into the livers of rabbits bearing VX2 liver cancer. This procedure was followed by 15 Gy electron irradiation. Evaluation of tumour volume and histological examination was carried out on the 7th day after treatment. The greatest tumour response was obtained in the group which received MISO followed by radiation and was characterised by extensive fibrosis around the tumour and nearly complete tumour necrosis. Liver cell regeneration was also noted in adjacent liver tissue. The advantages of regional infusion of MISO following hepatic-arterial embolisation are: (1) Selectivity increased radiosensitivity of liver cancer alongside very low drug concentration in the plasma. (2) Reduced or absent deleterious side effects of MISO with higher tumour/normal tissue ratios of drug concentration. (3) Reduced cost due to the lower dosage of MISO required for regional infusion.

Animals↗
PubMed1992

An examination of the effects of double-strand breaks on extrachromosomal recombination in mammalian cells.

We studied the effects of double-strand breaks on intramolecular extrachromosomal homologous recombination in mammalian cells. Pairs of defective herpes thymidine kinase (tk) sequences were introduced into mouse Ltk- cells on a DNA molecule that also contained a neo gene under control of the SV40 early promoter/enhancer. With the majority of the constructs used, gene conversions or double crossovers, but not single crossovers, were recoverable. DNA was linearized with various restriction enzymes prior to transfection. Recombination events producing a functional tk gene were monitored by selecting for tk-positive colonies. For double-strand breaks placed outside of the region of homology, maximal recombination frequencies were measured when a break placed the two tk sequences downstream from the SV40 early promoter/enhancer. We observed no relationship between recombination frequency and either the distance between a break and the tk sequences or the distance between the tk sequences. The quantitative effects of the breaks appeared to depend on the degree of homology between the tk sequences. We also observed that inverted repeats recombined as efficiently as direct repeats. The data indicated that the breaks influenced recombination indirectly, perhaps by affecting the binding of a factor(s) to the SV40 promoter region which in turn stimulated or inhibited recombination of the tk sequences. Taken together, we believe that our results provide strong evidence for the existence of a pathway for extrachromosomal homologous recombination in mammalian cells that is distinct from single-strand annealing. We discuss the possibility that intrachromosomal and extrachromosomal recombination have mechanisms in common.

Animals↗
PubMed1992

[Expression of gene products of insulin-like-growth-factor II, insulin-like-growth-factor II receptor and colony-stimulating-factor-I receptor in human primary hepatocellular carcinoma and non-cancerous liver tissues].

Western blot technique was used to detect the expression of gene products of IGF-II and IGF-II receptor as well as CSF-1 receptor in hepatocellular carcinoma and its adjacent nontumours liver tissue. A fetal expression of IGF-II was noted in 33 KD. IGF-II receptor was expressed in 260 KD and 230 KD with mature and immature forms, and CSF-1 receptor in 180 KD, 139KD and 122KD with different forms. The close relationship between the synthesized regulation and overexpression of three gene protein products and hepatocarcinogenesis was discussed.

Adult↗
PubMed1992

Immunoglobulin prophylaxis against HTLV-I in a rabbit model.

We have investigated the protective effect of human T-cell leukemia virus I (HTLV-I) immune globulin (HTLVIG) against HTLV-I in rabbits. HTLVIG containing 77 mg/ml of IgG was prepared from pooled plasma from seropositive healthy persons. In the first experiment, four groups (A, B, C, and D) of three rabbits were transfused with 5 ml blood from an HTLV-I-infected rabbit. Groups A, B, and C were infused 24 h later with 10, 5, and 2 ml HTLVIG, respectively, while group D was infused with 10 ml HTLVIG 48 h later. Seroconversion for HTLV-I occurred in none of group A, one of group B, and all of groups C and D after 2-5 weeks. In the second experiment, four litters (E, F, G, and H) born to another virus-infected rabbit and consisting of 7, 5, 7, and 7 newborns, respectively, were used. Litters E and H were allowed to grow normally as controls, while litters F and G were given intraperitoneal inoculation of 3 ml/kg of HTLVIG weekly four times until weaning. Although three of litters E and H each seroconverted after 5-8 weeks, none of litters F, and one of litter G became antibody-positive after 10 weeks. Presence or absence of HTLV-I infection in all these animals was confirmed by transfusion assay or gene amplification. These results indicate that passive immunization protects rabbits against blood- and milk-borne transmission of HTLV-I.

Animals↗