Biomedical subjects

L Yau

Publications and source records attributed to L Yau.

4 recordsLinked to original sources

PubMed1996

Inhibition of RNA synthesis by bradykinin involves both the B1 and B2 receptor subtypes.

The efficacy of angiotensin converting enzyme inhibitors in the treatment of heart disease is due in part to the accumulation of bradykinin (BK). Since BK can exert its effect by influencing cell proliferation, we chose to study the effect of BK on the growth of A10 vascular smooth muscle cells. Ligand binding studies to determine which BK receptor subtypes are present on A10 cells showed that both B1 and B2 receptors were present in approximately equal numbers. Examination of RNA synthesis demonstrated that BK inhibits uridine incorporation in a dose-dependent manner. This decrease in RNA synthesis was blocked by both B1 and B2 receptor antagonists, as well as by addition of indomethacin, a cyclooxygenase inhibitor. The latter result suggested that prostaglandins mediate the biological actions of BK. Consequently, we examined the direct effect of two prostaglandins, PGE2 and PGI2 (prostacyclin), on A10 cells. PGE2 caused a decrease in RNA synthesis, thus mimicking the effect of BK, while PGI2 did not. Therefore, the inhibition of RNA synthesis in A10 vascular smooth muscle cells by BK requires both B1 and B2 receptor subtypes and this action of BK is apparently mediated by de novo synthesis of prostaglandins.

Animals↗

PubMed1994

ADP-ribosylation and gene expression.

Gene expression can be defined as the conversion of information existing in a molecule of DNA into a mature RNA or protein product and each step in the process, which requires the concerted action of several macromolecules for completion, may be perturbed by the post-translational modification of specific proteins with ADP-ribose. The participation of poly(ADP-ribose) in the regulation of transcription initiation was examined using cell-free systems for both ribosomal RNA and ribosomal proteins. The presence or absence of poly(ADP-ribose) polymerase did not influence the transcription process. Similarly, under conditions optimal for poly(ADP-ribose) polymerase activity, no change in transcription was observed. A direct contribution of poly(ADP-ribosyl)ation to gene transcription thus could not be detected. In contrast, the addition of 3-aminobenzamide to quiescent hepatoma cells treated with insulin inhibited the stimulation of rRNA synthesis. The high concentrations necessary for this effect suggest that a mono(ADP-ribosyl)ation event participates in the cellular action of insulin. A role in the signal transduction pathway leading to activation of rRNA gene expression has been proposed.

ADP Ribose Transferases↗

PubMed1989

A microcomputer-based, net-lending interlibrary loan system.

A microcomputer-based, net-lending interlibrary loan system was developed at Lane Medical Library, Stanford University. The system, designed to generate the monthly billing invoices and all necessary statistical reports, has reduced the time required for logging-in procedures and compilation of monthly, quarterly, and annual statistics. User menus, help screens, and choice fields were developed explicitly for library staff who have little or no computer experience. The program was written using the DataEase database management software running on IBM PC, XT, AT, or compatible with a minimum of 512K RAM. Described are features of this automated interlibrary loan management system and its use in a net-lending interlibrary loan department. It focuses on data entry in the "Library Directory" and "ILL Log Sheet," details of billing invoices, and statistical reports, and flexibility in modifying tax rates, borrowing fees, and other parameters.

Accounting↗

PubMed1980

Long term effects of perinatal injection of estrogen and progesterone on the morphological and biochemical development of the mammary gland.

The effects of neonatal injection of estrogen and progesterone on the subsequent in vitro hormone responsiveness of murine mammary glands were determined by a coordinated study of the morphological development and the biochemical response of explants. After daily in vivo pretreatment with estrogen and progesterone, explants were cultured for 5 days in a chemically defined medium containing insulin alone or insulin, cortisol, and PRL. After the culture period, the morphological development of alveoli and lobules was rated. In addition, casein mRNA was quantitated using a specific complementary DNA hybridization probe. Perinatal 17 beta-estradiol exposure was found to increase casein mRNA content as well as lobular development. Conversely, perinatal progesterone treatment inhibited both casein mRNA induction and the formation of lobules. The administration of both estradiol and progesterone to newborns resulted in an antagonistic response between these two steroids, and there was no effect on casein mRNA levels or lobular development in comparison with untreated controls. Mammary tissues of perinatally estrogen-treate mice displayed greater lobular development and contained higher levels of casein mRNA in response to an extension of the duration of in vivo pretreatment from 6 to 9 days. A comparison of the PRL dose response in vitro suggested that exposure to estrogen perinatally sensitized the mammary tissue to the subsequent addition of PRL in culture. These studies indicate that injection of newborns with estrogen may enhance the subsequent hormonally regulated differentiation of the mammary gland. Exposure to progesterone may inhibit later development, and both steroids in combination may exert antagonistic effects. These effects were not mediated solely by alterations in the normal endocrine status of the treated animals but were reflected by the subsequent hormonal response of mammary explants in a defined culture medium. This altered sensitive to hormones may be important in the increased incidence of mammary dysplasias observed in these animals.

Animals↗