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Biomedical subjects

Y He

Publications and source records attributed to Y He.

At least 397 records · Page 22Linked to original sources
PubMed1994

Stress relaxation of fibroblasts activates a cyclic AMP signaling pathway.

Mechanical force regulates gene expression and cell proliferation in a variety of cell types, but the mechanotransducers and signaling mechanisms involved are highly speculative. We studied the fibroblast signaling mechanism that is activated when cells are switched from mechanically stressed to mechanically relaxed conditions, i.e., stress relaxation. Within 10 min after initiation of stress relaxation, we observed a transient 10-20-fold increase in cytoplasmic cyclic AMP (cAMP) and a threefold increase in protein kinase A activity. The increase in cAMP depended on stimulation of adenylyl cyclase rather than inhibition of phosphodiesterase. Generation of cAMP was inhibited by indomethacin, and release of arachidonic acid was found to be an upstream step of the pathway. Activation of signaling also depended on influx of extracellular Ca2+ because addition of EGTA to the incubations at concentrations just sufficient to exceed Ca2+ in the medium inhibited the stress relaxation-dependent increase in free arachidonic acid and cAMP. This inhibition was overcome by adding CaCl2 to the medium. On the other hand, treating fibroblasts in mechanically stressed cultures with the calcium ionophore A23187-stimulated arachidonic acid and cAMP production even without stress relaxation. In summary, our results show that fibroblast stress relaxation results in activation of a Ca(2+)-dependent, adenylyl cyclase signaling pathway. Overall, the effect of stress relaxation on cAMP and PKA levels was equivalent to that observed after treatment of cells with forskolin.

1-Methyl-3-isobutylxanthine↗
PubMed1994

Uptake, transport and metabolism of exogenous nucleosides in intestinal epithelial cell cultures.

The uptake and transport of nucleosides (adenosine, cytidine, guanosine, thymidine, uridine and inosine) were examined in intestinal cell lines (Caco-2 and IEC-6). Well-differentiated Caco-2 cells took up significantly more uridine and thymidine than less-differentiated cells over 24 h. These differences were reflected in the resulting trichloroacetic acid-soluble (nucleotide, nucleoside and nucleobase) pool sizes rather than in differences in nucleic acid incorporation. IEC-6 cells have smaller soluble pools than Caco-2 cells, and the uptake of nucleosides over 60 min reflected this difference. Caco-2 cells transported significantly more thymidine, cytidine, guanosine, adenosine and inosine into acid-soluble pools than IEC-6 cells. Caco-2 cells were grown on filters to examine the transcellular transport of nucleosides and to examine the chemical form in which nucleosides appeared at the basolateral aspect of the cell monolayer. The pattern of transport varied for individual nucleosides. The transport of cytidine and guanosine was significantly greater in the apical-to-basolateral direction than in the opposite direction over 2 h. No purine nucleoside was transported intact across the Caco-2 cell monolayer in either direction, with the majority of the transported material appearing as nucleobases. Nucleobases also represented the main metabolites of pyrimidines transported. However, some cytidine and uridine were detectable, but each constituted < 20% of transported material. Nucleosides are therefore transported by enterocytes but metabolized during transport.

Adenosine↗
PubMed1994

Nucleotide uptake and metabolism by intestinal epithelial cells.

The epithelial cells of the gastrointestinal tract are the first to encounter ingested nucleotides. Enterocytes metabolize or transport nucleotides (often partially metabolized) to other cell types. Nucleotides may also affect enterocyte gene expression. These interactions in intestinal cell lines (Caco-2 and IEC-6 cells) are described. Nucleotides and nucleosides are efficiently taken up by neoplastic cells (Caco-2) and substantially metabolized during absorption by epithelial monolayers. In nonmalignant cells (IEC-6), nucleotide pools are smaller than enterocytes of neoplastic origin (Caco-2). Consequently, cell proliferation in IEC-6 cells is more dependent on an external supply of nucleotides. Cell differentiation was examined by measuring brush border enzyme activities (sucrase, lactase and alkaline phosphatase). Nucleotides enhanced the expression of brush border enzymes in carcinoma cells only when stressed by glutamine deprivation. IEC-6 cells, which are poorly differentiated in optimal media, require basement membrane (Matrigel) for expression of brush border enzymes. Under these conditions, adding nucleotides to the culture medium enhanced enzyme activity. In addition to being substrates for intestinal absorption, nucleotides may affect enterocyte differentiation.

Adenosine Monophosphate↗
PubMed1994

[Neuropathology of 20 centenarians. I. Clinical data].

We report a clinical study of 20 patients aged more than 100 years, and deceased in Charles Foix Hospital, Ivry/Seine, France, where they had stayed for 10 days to 16 years (mean: 3.3 years, median: 4 years). Each of them was studied neuropathologically (the results of this study will be published later on). The case selection excluded only those patients whose neuropathological study could not be complete. The prevalence of sensorial deficits was high: 15/20 patients had deterioration of hearing, 8 of them were deaf; 14/20 patients had deterioration of sight, 4 of them were blind. Motor deficits were numerous: 15 patients were not ambulatory. The patients were classified as demented or not, according to the criteria of the DSMIII R (American Psychiatric Association 1987), on the basis of a retrospective evaluation of clinical records, and of an inquiry among the caring staff. Their mental status was also evaluated by the Global Deterioration Scale of Reisberg et al (1985). Five patients had been demented, four had been intellectually normal, and 11 had suffered from mild disturbances of memory or cognitive functions. This series was not representative of the general population of centenarians, but probably of those institutionalized in France. We observed a low proportion of demented patients despite the prevalence expected from epidemiological studies. This is difficult to interpret. The low proportion of dementia in this small sample is not due to the short duration of the course of diseases responsible for dementia.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1994

[A clinic report of 54 cases of reconstruction for the anterior segment of eye].

54 cases (54 eyes) of severe injury in the anterior segment of eye with little light perception were treated by reconstruction for the anterior segment of eye. The results showed that the eyeballs in 48 cases (88.9%) were survived successfully, and 28 cases (51.9%) of the grafts were clear. The procedures included keratoplasty, iridectomy, lensectomy, anterior vitrectomy, and reconstruction of the anterior chamber to restore the cosmetic shape of the eyeball. The indications, complications of the operation, and the surgical technique are discussed.

Adolescent↗
PubMed1994

Schistosoma japonicum: size of egg granulomas in vaccinated and non-vaccinated hosts as observed in bovines.

The present paper reported the results of studies on the size of Schistosoma japonicum egg granulomas in susceptible and poorly susceptible, vaccinated and non-vaccinated, hosts as observed in bovines. It was noted that in both cattle and buffaloes, the mean size of the granuloma was smaller in vaccinated than in the non-vaccinated. The vaccinated bovines will accordingly not only be benefited by the reduction of the survival rate of the challenged schistosomula but also by decreasing the size of the egg granulomas.

Animals↗
PubMed1994

Effect of LFA-1 and ICAM-1 antibody treatment on murine corneal allograft survival.

PURPOSE: To examine the effect of anti-LFA-1 and anti-ICAM-1 antibody treatment on orthotopic corneal graft survival in a mouse model. METHODS: Anti-LFA-1 and anti-ICAM-1 antibodies were administered intraperitoneally before and shortly after orthotopic corneal transplantation. Grafts were observed by biomicroscopy, and survival times were determined. Cytotoxic T lymphocyte (CTL) and delayed-type hypersensitivity (DTH) responses to donor alloantigens were assessed at selected times after grafting. RESULTS: Administration of anti-LFA-1 antibody reduced the incidence of graft rejection from 90% in untreated donors to 47% in anti-LFA-1 treated mice. By contrast, treatment with anti-ICAM-1 antibody alone did not reduce the incidence of rejection, although it prolonged graft survival time. Both CTL and DTH responses to donor alloantigens were severely depressed in hosts treated with either anti-LFA-1 or anti-ICAM-1 antibody. However, neither anti-ICAM-1 nor anti-LFA-1 antibody treatment prevented the rejection of orthotopic corneal grafts in previously immunized mice. CONCLUSIONS: Anti-ICAM-1 antibody does not promote graft survival even though it impairs CTL and DTH responses to donor alloantigens. By contrast, anti-LFA-1 antibody can significantly reduce the incidence of orthotopic corneal graft rejection and prevent the induction of normal allospecific CTL and DTH responses. Although anti-LFA-1 antibody is effective if given prophylactically, it is ineffective at preventing corneal graft rejection in previously immunized hosts.

Animals↗
PubMed1994

Nonidentified responses in a proportional hazards setting.

Nonidentified response (NR), an important form of nonindependent censoring, is modelled in a proportional hazards setting. Methods to test for existence of and identify NR censored observations are developed. Incorporation of NR censoring information into appropriate algorithms can improve parameter and underlying baseline hazard estimation. Application to estimating time until death from AIDS is made.

Acquired Immunodeficiency Syndrome↗
PubMed1994

[Morphology and phagocytic activity of hemocytes of Oncomelania hupensis].

Hemocytes from Oncomelania hupensis hemolymph were studied in vitro. Spreading amoebocytes were the most common cell type. The average sizes of amoebocytes from Anhui and Yunnan were 8.42 +/- 0.73 x 7.46 +/- 0.52 microns and 7.63 +/- 0.65 x 6.85 +/- 0.54 microns, respectively. The nucleus was round in shape, and eosinophile granular inclusions were found in the endocytoplasm. Contacting with slide, the cells became flattened with extending pseudopodia. The ability of amoebocytes from snails of both localities to phagocytose sheep red blood cells was confirmed in vitro. The method to collect hemolymph from Oncomelania hupensis was developed, and the promise of this method in studying host-parasite relationship as well as epidemiological investigation of schistosomiasis japonica in the mainland of China was discussed.

Animals↗
PubMed1994

Factors influencing survival after AIDS: report from the Multicenter AIDS Cohort Study (MACS).

The objective of this study was to determine if clinical signs, symptoms, laboratory variables, and use of therapeutic or prophylactic agents have prognostic associations with survival after diagnosis of clinical AIDS. A total of 2,168 homosexual men, seropositive for human immunodeficiency virus type 1 (HIV-1) participated in a longitudinal cohort study of the greater metropolitan areas of Baltimore, Maryland, Washington, D.C., Chicago, Illinois, Pittsburgh, Pennsylvania, and Los Angeles, California, U.S.A.--the Multicenter AIDS Cohort Study (MACS). Variables within 6 months prior to AIDS diagnosis included age, CD4+ lymphocyte counts, hemoglobin, and self-reported thrush, fever, anti-retroviral therapy (ART) beginning prior to AIDS onset, and ART beginning after AIDS (as a time-dependent covariate) were analyzed as mutually exclusive categories, as was prophylaxis for Pneumocystis carinii pneumonia (PCP). Univariate and multivariate survival models of time from AIDS to death were fit. In univariate analysis, younger age, higher counts of CD4+ lymphocytes, hemoglobin, and absence of thrush or fever prior to AIDS onset were associated with longer survival after AIDS. Those who began ART within 3 months after AIDS onset had longer median survival (1.75 years), from 3 months after AIDS, when compared with those who began ART prior to AIDS (1.18 years). This comparison is not influenced by the bias that those who survive longer have a greater likelihood to subsequently receive ART. Prophylaxis for PCP beginning after AIDS onset was also associated with longer post-AIDS survival when compared with beginning prophylaxis prior to AIDS or never using prophylaxis.(ABSTRACT TRUNCATED AT 250 WORDS)

Acquired Immunodeficiency Syndrome↗
PubMed1993

Correlation between the inhibition of cell growth by accumulated polyamines and the decrease of magnesium and ATP.

The mechanism of the antiproliferation effect of spermidine and spermine was studied using a cell culture system of mouse FM3A cells. The addition of either 10 mM spermidine or 2 mM spermine to the growth medium containing 0.9 mM Mg2+ greatly inhibited cell growth (more than 90%). A decrease in the Mg2+ concentration to 50 microM in the growth medium, but without the polyamine addition, did not influence cell growth. However, the concentrations of spermidine and spermine necessary for the inhibition of cell growth when cells were cultured in the presence of 50 microM Mg2+ were much smaller (2 mM spermidine and 0.15 mM spermine). Nevertheless, the amount of polyamines accumulating in cells which could cause the inhibition of cell growth was almost the same, regardless of the large difference in the added polyamine concentrations. At the early stage of polyamine accumulation, the inhibition of cell growth correlated with the decrease of Mg2+ content, but not with a decrease of the ATP content. The decrease in Mg2+ content correlated well with the inhibition of macromolecular synthesis, especially protein synthesis. Thus, the inhibition of cell growth at the early stage of polyamine accumulation was thought to be due to the inactivation of ribosomes through the replacement of Mg2+ on magnesium-binding sites by polyamines. The decrease in Mg2+ content was mainly caused by the inhibition of Mg2+ transport by polyamines. At the later stage of polyamine accumulation, a decrease in ATP content was also observed. This was followed by swelling of the mitochondria, which may be a symptom of the subsequent cell death.

Adenosine Triphosphate↗
PubMed1993

On the structure of calonyctin A, a plant growth regulator.

The plant growth regulator calonyctin A, isolated from the dried leaves of Calonyction aculeatum L. House (Yue-Guang-Hua), was separated into two pure components by high performance liquid chromatography. By use of mass spectrometry based on various ionization techniques, one- and two-dimensional NMR spectroscopy, IR spectrometry, and chemical methods the molecular structures of the two homologous glycosides were determined. Each molecule contains two hydroxy fatty acid residues and four 6-deoxyhexose units. The fatty acids are 3-hydroxy-2-methylbutanoic acid and 11-hydroxytetradecanoic acid or 11-hydroxyhexadecanoic acid. The 6-deoxyhexose residues (three of quinovose and one of rhamnose) comprise a tetrasaccharide having the following structure: [formula: see text] The long-chain hydroxy acid is linked glycosidically through its O-11 to Qui D and esterified to O-2 of Qui C, forming a macrocyclic lactone. The 3-hydroxy-2-methylbutanoic acid is ester-linked to O-3 of Qui C.

Carbohydrate Conformation↗
PubMed1993

Fourier transform Raman spectroscopy of the bacteriorhodopsin mutant Tyr-185-->Phe: formation of a stable O-like species during light adaptation and detection of its transient N-like photoproduct.

Near-infrared FT-Raman spectroscopy can be used to measure the vibrations of the bacteriorhodopsin (bR) chromophore without the disadvantage of conventional visible resonance Raman spectroscopy, where the visible excitation drives the bR photoreactions. We utilized this technique to investigate the light-dark adaptation of bacteriorhodopsin and the mutant Tyr-185-->Phe (Y185F) at room temperature in solution. Compared to wild-type bR, both the FT-Raman and resonance Raman spectra of the light-adapted Y185F displayed new features characteristic of the vibrations of the O intermediate. Light adaptation of Y185F was found to involve a 13-cis, C=N syn-->all-trans isomerization of the retinal chromophore which produces a species similar to bR570 and a second O-like species. Dark adaptation, which was much slower in Y185F compared to wild-type bR, involved a parallel decay of the bR570 and O-like species and resulted in a decreased all-trans:13-cis ratio compared to wild type. Further evidence for the existence of an O-like species in Y185F comes from pump-probe Raman difference spectroscopy, where a red pump beam is found to produce a species very similar to the N intermediate in the photocycle. This species is shown by stroboscopic Raman measurements to exist transiently even at high pH. We postulate that when the Y185F chromophore has an all-trans structure the effective pKa of Asp-85 and Asp-212 is elevated in Y185F due to the disruption of the Asp-212/Tyr-185 hydrogen bond, thereby accounting for the increased protonation of these residues in the O-like species.

Bacteriorhodopsins↗