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Biomedical subjects

S Yang

Publications and source records attributed to S Yang.

At least 577 records · Page 32Linked to original sources
PubMed1993

[Morphometric evaluation on the pathologic changes in ovariectomized endometria influenced by estrogen use].

Thirty SD female rats were divided into the following groups: (1) sham operation; (2) bilateral ovariectomized (OVX); (3) OVX and estrogen-treated (E). Computerized Image Analyser was used to evaluate the pathologic changes of endometria in these animals. The results showed the endometria of OVX group was in the state of atrophia, while the endometria of E group was in the state of early proliferative stage. The heights of endometria, endometrial epithelia cells and gland epithelia cells, the volume fraction and numerical density of endometrial glands, and the cavity diameter of the glands could effectively express the proliferative changes of the endometria. It is suggested that this method be used to study the pathology of the different endometric diseases.

Animals↗
PubMed1993

Epidermal growth factor-like growth factors. I. Breast malignancies and other epithelial proliferations in transgenic mice.

BACKGROUND: Growth factors recognized by the epidermal growth factor receptor are important in tumor production in some organs. The family of epidermal growth factor-like growth factors includes a group of poxviral growth factors: Shope growth factor (SGF), myxoma growth factor MGF), and vaccinia growth factor. These viral growth factors are glycoproteins, whereas all other members of the epidermal growth factor family are proteins. EXPERIMENTAL DESIGN: To understand the potential significance of poxviral growth factors, we made transgenic mice using three different constructs: SGF and MGF cloned downstream from the metallothionein (MT) promoter (MTSGF), and SGF downstream from Rous sarcoma virus long terminal repeat. RESULTS: Founder transgenic mice for each construct were identified, and lines established. Expression of transgenes in MT-SGF mice and MT-MGF mice was induced by feeding animals Zn at 2 months of age. Two months later, both MT-SGF and MT-MGF mice showed proliferation and arborization of breast ducts and ductules, with slight intraductal proliferation in virgin mice. They also showed gastric epithelial hyperplasia, particularly in MT-MGF mice. Stromal and epithelial hyperplasia were found in several organs. The transgenes were expressed in epithelia and stroma of breast, lungs, liver and stomach. Rous sarcoma virus long terminal repeat-SGF transgenic mice developed atypical preneoplastic mammary ductal proliferations in both virgin and nonvirgin females by 6 months of age. In 1/3 of 8-month-old females, invasive secretory adenocarcinoma developed. These mice also developed severe epithelial atypia in the stomach, and papillary gastric tumors. CONCLUSIONS: Poxviral growth factors may thus be helpful in the study of mammary and gastric oncogenesis and provide insight into growth factor-induced tumor development.

Animals↗
PubMed1993

The immunosuppressive effects of dexamethasone administered in drinking water to C57BL/6N mice infected with Cryptosporidium parvum.

The feasibility of immunosuppressing adult C57BL/6N mice by using dexamethasone in drinking water to sustain infections with Cryptosporidium parvum was investigated. An ethanol-soluble formulation of dexamethasone (DEX) was compared with a water-soluble (phosphated) formulation (DEXp). DEX or DEXp was provided for mice ad libitum in drinking water at dosages of 10, 33, and 100 micrograms/ml. DEX was also administered to mice by intraperitoneal injection at 125 micrograms/mouse/day. All mice were inoculated intragastrically with 10(6) C. parvum oocysts/mouse on day 14 postimmunosuppression. Mice immunosuppressed through drinking water exhibited increased signs of toxicity compared with mice intraperitoneally injected with DEX. Moreover, mice receiving DEX in drinking water were less active and died significantly sooner (P < 0.05) than mice receiving DEXp at the same dosages. Immunosuppressed mice began shedding oocysts 3 days postinfection and continued to shed until they either died or were killed. Beginning on day 12 postinfection, mice receiving DEX or DEXp in drinking water shed significantly more oocysts (P < 0.05) than mice immunosuppressed via intraperitoneal injection. Immunosuppressing mice through drinking water was comparatively simple, less traumatic than injection, and efficient with regard to time and labor.

Administration, Oral↗
PubMed1993

[Nilestriol prevents osteoporosis in ovariectomized rats].

In order to determine the effects and mechanism of Nilestriol upon bone metabolism, 4-month aged female SD rats were divided randomly into three groups: The OVX group subjected to bilateral ovariectomy, the SHAM group to sham operation, the Nilestriol (CEE3) group to bilateral ovariectomy and treated with CEE3 0.15 mg/100 g BW once a week for 10 weeks. The CEE3 was introduced directly into the stomach from the first day after operation. All rats were killed 10 weeks after operation and their right proximal tibiae were processed undercalcified for quantitative bone histomorphometry. The weights of bone and inorganic matter (ash content) and content of calcium, phosphorus of right humeral were measured. The results showed that in the OVX group the trabecular bone volume, the trabecular thickness, the content of calcium bone, and the ratios of bone weight and ash weight to body weight were all significantly reduced. The bone loss was associated with an increase in bone remodeling; the bone resorption appeared much more marked than the bone formation. In contrast, the ovariectomized animals treated with CEE3 had normalization of bone mass and a declined index of bone resorption and formation which recovered the balance of bone remodeling. It suggested that CEE3 is successful in prevention of bone loss in OVX rats. It is convinced of using Nilestriol to prevent postmenopausal osteoporosis.

Animals↗
PubMed1992

The receptor-binding site of human relaxin II. A dual prong-binding mechanism.

Recent structure/function studies on human relaxin II have led to the conclusion that the arginines B13 and/or B17 are important for biological activity. These studies have been confirmed and extended with the help of chemically synthesized derivatives, i.e. dicitrulline (B13, B17), two monocitrulline (B13 and B17), a dilysine (B13, 17), and alanine (B17) relaxins. The CD spectra of synthetic human relaxin and of the derivatives are indistinguishable. Yet, only the native human relaxin II is biologically active and binds strongly to relaxin receptor preparations in vitro. The inactivation is strictly due to side chain functions, in particular the replacement of either or both arginines in the positions B13 or B17. Binding is mediated by a two-prong electrostatic and hydrogen-binding interaction via arginines B13 and B17. Neither B13 nor B17 alone are sufficient and a positive charge equidistant from the B chain helix is equally insufficient. This binding mechanism appears to be unique, as concerns hormone receptor interaction.

Amino Acid Sequence↗
PubMed1992

Comparison of CNS homing pattern among murine TH cell lines responsive to myelin basic protein.

A myelin basic protein (MBP)-reactive TH cell line capable of inducing experimental allergic encephalomyelitis (EAE), and a MBP-reactive TH cell clone that does not cause EAE were labeled with a fluorescent vital dye, and transferred into naive syngeneic SJL/J mice. Animals were killed before the appearance of symptoms (3 and 4 days post-injection). Sections obtained from the spleen, spinal cord and brain of both groups of animals were examined by fluorescence microscopy to localize labeled TH cells. At all time points examined, the spleens of both groups contained innumerable labeled cells. The spinal cords and brains of animals that had received EAE-causing cells had a basal level of 20 labeled cells/cm2 at 3 days; this number increased rapidly to 150 cells/cm2 in the spinal cord at 4 days. Perivascular infiltrates and small foci of astrogliosis were already apparent in this group 3 days after injection. The spinal cords and brains of animals that had received the non-EAE-causing TH cells contained 50 labeled cells/cm2 at 3 days. The density of these transferred cells, as compared to that of the EAE-causing cells, suggested that they have an unaltered CNS-homing capability. However, by 4 days, the number of non-EAE-causing labeled cells had returned to near basal level. Our findings suggest that discrimination between disease and non-disease causing MBP-responsive TH cells occurs within the first 3 days following transfer, requires the presence in the CNS of a limited number of TH cells, and depends on yet unidentified TH cell factor(s).

Animals↗
PubMed1992

Hydraulic Conductivity Recovery versus Water Pressure in Xylem of Acer saccharum.

Experiments were conducted to determine the influence of stem diameter, xylem pressure potential, and temperature on the rate of recovery of hydraulic conductivity in embolized stems of Acer saccharum Marsh. Recovery of conductivity was accompanied by an increase in stem water content as water replaced air bubbles and bubbles dissolved from vessels into the surrounding water. The time required for stems to go from less than 3 to 100% hydraulic conductivity increased approximately with the square of the stem diameter and increased with decreasing xylem pressure potential. Recovery was halted when xylem pressure potential decreased below -6 kPa. Increasing xylem pressure from 13 to 150 kPa reduced the time for recovery by a factor of 4. Temperature had little influence on the rate of recovery of hydraulic conductivity. All of these results are in accord with a theory of bubble dissolution in which it is assumed that: (a) the rate of bubble dissolution is rate limited by diffusion of air from the bubbles to the outer surface of the stems, (b) the equilibrium concentration of gases in liquid in stems is determined by Henry's law at all air-water interfaces, (c) the equilibrium solubility concentration is determined only by the partial pressure of the gas in the gas phase and not directly by the liquid-phase pressure, and (d) the gas pressure of an entrapped air bubble in the lumen of a cell can never be less than atmospheric pressure at equilibrium.

Journal Article↗
PubMed1992

Human colon cancer cells express ICAM-1 in vivo and support LFA-1-dependent lymphocyte adhesion in vitro.

Intercellular adhesion molecule-1 (ICAM-1) is a cell surface adhesion glycoprotein that mediates leukocyte adhesion through interaction with the leukocyte CD11/CD18 adhesion complex. The aim of this study was to determine whether ICAM-1 is expressed by normal or neoplastic colonic epithelial cells. Immunohistochemical studies on human colonic tissue demonstrated focal ICAM-1 expression by colonic carcinomas but not by normal colonic epithelium. ICAM-1 expression by colonic carcinomas showed a positive correlation with the presence of a peritumoral inflammatory infiltrate. Surface expression of ICAM-1 was also observed in HT-29 cultured human colon cancer cells by both immunohistochemistry and enzyme immunoassay. Interferon-gamma and interleukin-1 beta significantly increased ICAM-1 surface expression by HT-29 cells in a dose-dependent manner. Upregulation of ICAM-1 surface expression became evident some hours after cytokine stimulation and was inhibited by both actinomycin D and cycloheximide, indicating a requirement for de novo RNA and protein synthesis. HT-29 monolayers supported adhesion of human lymphocytes as determined by a quantitative 111In-labeled leukocyte adhesion assay. Adhesion was mediated in part via interaction of ICAM-1 on HT-29 cells with lymphocyte function-associated antigen-1 (CD11a/CD18) on lymphocytes, as defined by using blocking monoclonal antibodies. Expression of ICAM-1 and/or other leukocyte adhesion receptors by neoplastic epithelial cells may play a role in directing leukocyte trafficking and leukocyte-epithelial cell interactions in colonic carcinoma.

Carcinoma↗
PubMed1992

Relaxin receptors in mice: demonstration of ligand binding in symphyseal tissues and uterine membrane fragments.

A monocomponent, high specific activity, carrier-free porcine relaxin tracer (125I) has made it possible for us to demonstrate relaxin receptors in the symphysis pubis, uterus, and ovary via autoradiography. The receptors are concentrated in the symphyseal ligament and the peripheral layers of uterus and ovary. Specific relaxin binding was observed in crude membrane preparations of uteri, ovaries, and brain, whereas crude membranes of leg muscle and kidney showed only nonspecific binding. Uterine membranes prepared from estrogen-primed mice showed tracer binding, which could be significantly inhibited by porcine relaxin in a dose-dependent manner, but not by insulin. A linear Scatchard plot suggested the presence of only one kind of receptor and a dissociation constant of 5 x 10(-10) M, which is commensurate with an electrostatic double ion pair binding mechanism.

Animals↗
PubMed1992

Cellular distribution of a colonic adenoma-associated antigen as defined by monoclonal antibody Adnab-9.

Adenomatous colonic polyps constitute a precursor for colorectal cancer. Antibodies to these precancerous lesions might identify specific early tumor antigens. Adnab-9 is a murine monoclonal antibody raised against membranes of colonic adenomas. Adnab-9 binding in colonic washings (effluent) correlates with the presence of colorectal cancer. Immunohistochemical staining with Adnab-9 shows cytoplasmic reactivity in scattered cells in 4 of 31 adenomatous tissue sections, 0 of 14 sections of colorectal cancer cells, and 1 of 8 normal-appearing colonic mucosa specimens examined. Adnab-9 recognized a dominant M(r) 87,000 protein species in tissue extracts in the membrane-bound fraction of effluent by Western blotting. Adnab-9 binding by enzyme-linked immunosorbent assay in adenomatous extracts is higher than cancer or normal tissue, is membrane-bound, and is absent from established colorectal cancer cell lines. This distribution and nature of immunostaining suggest that Adnab-9 recognizes a determinant associated with the membrane component of a subpopulation of adenoma cells which may have a role in early colorectal neoplasia.

Adenoma↗