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Biomedical subjects

G Yu

Publications and source records attributed to G Yu.

At least 235 records · Page 13Linked to original sources
PubMed1993

Identification and genetic analysis of Schizosaccharomyces pombe cDNAs that suppress deletion of IRA1 in Saccharomyces cerevisiae.

Ira1 is a negative regulator of Ras proteins in Saccharomyces cerevisiae. Deletion of IRA1 leads to constitutive activation of the Ras/cyclic AMP (cAMP) pathway, which results in several phenotypes including sensitivity to heat-shock (HS) treatment. We have identified eight Schizosaccharomyces pombe cDNAs that, when overexpressed, suppress the HS-sensitive phenotype associated with the deletion of IRA1 in S. cerevisiae. To determine where these cDNAs act, we tested their ability to suppress other mutations that activate the Ras/cAMP pathway in S. cerevisiae. Two of the cDNA clones, pPSI1 and pPSI2, failed to suppress the HS-sensitive phenotype induced by the activating RAS2Val19 mutation. Clone pPSI2 encodes Gap1/Sar1, a Sz. pombe homologue of Ira1, which has been previously identified. Three of the six RAS2Val19 suppressors could suppress the deletion of PDE1 and PDE2, the cAMP phosphodiesterase (Pde)-encoding genes, suggesting that they act downstream from adenylyl cyclase (Cyr). The remaining three clones, pPSI3, pPSI6 and pPSI7, encode proteins that may suppress the HS-sensitive phenotype by reducing Ras and/or Cyr activity. One of these, pPSI3, contains a cDNA that encodes the C-terminal region (aa 166-550) of the Sz. pombe Dbp2 protein, a homologue of the human p68 RNA helicase. We have amplified cDNAs encoding the full-length Sz. pombe Dbp2 protein by the polymerase chain reaction method and have cloned them into a S. cerevisiae expression vector. The ira1- cells harboring these plasmids retained their HS-sensitive phenotype. These results suggest that the truncated Dbp2, but not the full-length protein, is capable of interfering with Ras and/or Cyr activity.

Amino Acid Sequence↗
PubMed1993

Phosphorylation of HIV-1 gag proteins by protein kinase C.

We have demonstrated that the 17-kDa N-terminal matrix protein (p17gag) of HIV-1 Pr55gag is a substrate for protein kinase C (PKC). Phosphorylation of p17gag and Pr55gag was studied in vivo by infecting COS-7 cells with a recombinant vaccinia virus containing the HIV-1 gag-pol gene. Basal gag protein phosphorylation was inhibited up to 75% with the PKC inhibitor, H-7, and stimulated 3-4-fold with phorbol 12-myristate 13-acetate. In experiments using MCF-7 cell lines, p17gag and Pr55gag were dramatically phosphorylated only in clones with high PKC activity. Bacterially expressed and purified non-myristoylated and N-myristoylated p17gag were efficiently phosphorylated in a Ca2+ and phosphatidylserine-dependent manner by purified PKC. The N-myristoylated p17gag exhibited an apparent Km = 4 microM for PKC phosphorylation. Both in vitro and in vivo phosphorylated p17gag yielded identical V8 protease digestion phosphopeptide maps, indicating identical PKC phosphorylation sites. Phosphoamino acid analysis of the in vitro phosphorylated p17gag revealed only phosphoserine. These data are consistent with the identification of a highly conserved consensus PKC phosphorylation site motif in the HIV-1 gag protein at Ser111 and suggests that PKC phosphorylation plays an important role in gag protein function.

Gene Products, gag↗
PubMed1993

Integration of murine leukemia virus DNA depends on mitosis.

In synchronized rat or mouse cells infected with Moloney murine leukemia virus (MLV), integration of viral DNA and production of viral proteins occur only after the cells traverse mitosis. Integration is blocked when cells are prevented from progressing through mitosis. Viral nucleoprotein complexes isolated from arrested cells contain full-length viral DNA and can integrate this viral DNA in vitro, showing that the block to integration in arrested cells is not due to a lack of mature integration machinery. When infected cells traverse mitosis, there is a sharp increase in nuclear accumulation of viral DNA. The dependence of integration on mitosis may therefore be due to a requirement for mitosis and nuclear envelope breakdown for entry of the viral integration complex into the nucleus.

Animals↗
PubMed1993

Severe constipation with diffuse intestinal myenteric hyperganglionosis.

The authors report a case of neuronal intestinal dysplasia in a 6-year-old girl. The disease is characterized by hyperplastic ganglia throughout the large and small intestine, associated with severe constipation. To better understand the pathophysiology of this disease the authors investigated the histopathologic, ultrastructural, and immunohistochemical characteristics of the intestinal tissue in this case. The hyperganglionosis was associated with immunohistochemical findings of intact expression of the neuropeptides controlling the peristaltic reflex, through lower expression of calcitonin-gene related peptide. With the recent progress in our understanding of the neural regulation of gastrointestinal function, it may now be possible to begin to understand the complex pathophysiological mechanisms underlying gastrointestinal motility disorders.

Calcitonin Gene-Related Peptide↗
PubMed1993

Vaginal reconstruction with an island flap of the inferior epigastric vascular pedicle.

This paper presents a new method of vaginal reconstruction. On the basis of anatomic study, we designed an island flap obtained from the upper abdomen to carry the deep inferior epigastric vasculature. At operation, the flap was transferred to the artificial cavity created between the urinary bladder and rectum for vaginal reconstruction. Eight patients received the operation. Complete survival of the flap occurred in seven patients, and one flap failed because of a twist in the flap vascular pedicle. During a follow-up of 6 months to 2 years, it was found that the reconstructed vaginal wall was not only soft but also elastic, and the patients were able to have a satisfying sexual life after marriage.

Adult↗
PubMed1993

SPT13 (GAL11) of Saccharomyces cerevisiae negatively regulates activity of the MCM1 transcription factor in Ty1 elements.

The Ty transposable elements of Saccharomyces cerevisiae consist of a single large transcription unit whose expression is controlled by a combination of upstream and downstream regulatory sequences. Errede (B. Errede, Mol. Cell. Biol. 13:57-62, 1993) has shown that among the downstream control sequences is a binding site for the transcription factor, MCM1. A small restriction fragment containing the Ty1 MCM1-binding site exhibits very weak activation of heterologous gene expression. The absence of SPT13 (GAL11) causes a dramatic increase in activity directed by these sequences. This effect is mediated through the MCM1-binding site itself. MCM1 mRNA and protein levels, as well as its affinity for its binding site, are unchanged in the absence of SPT13. Our results suggest that SPT13 has a role in the negative control of MCM1 activity that is likely to be posttranslational. A role for SPT13 in the negative regulation of the activity of the Ty1 MCM1-binding site is consistent with our previous proposal that spt13-mediated suppression of Ty insertion mutations could be attributed to the loss of negative regulation of genes adjacent to Ty elements.

Base Sequence↗
PubMed1993

[Protection of the ischemic myocardium].

The Authors review several pharmacological interventions aimed at protecting the ischemic myocardium. Drugs which have been widely used in the treatment of ischemic heart diseases, such as beta-blockers, nitrates and calcium-antagonists, are able to delay the development of ischemic injury if administered before the beginning of ischemia, but their clinical effectiveness is limited. The new drugs which are presently investigated are designed to counteract the molecular mechanisms which mediate irreversible tissue injury, namely cytosolic calcium overload, cellular hyperosmolarity, and free radical production. In particular, interventions able to interfere with the release of calcium from its intracellular stores would be of major importance. In this regards, it is interesting to point out that derivatives of phenylalkylamine calcium-antagonists have been reported to modulate the opening probability of sarcoplasmic reticulum calcium channels.

Adenosine↗
PubMed1993

[The correction of high AC/A ratio non-accommodative esotropia with straight-top bifocals].

82 juvenile cases of high AC/A ratio non-accommodative esotropia were treated with straight-top bifocals. The esotropia at near was corrected and the high AC/A ratio was controlled and gradually reduced with improved visual functions. The authors deemed the straight-top bifocals effective for correction of this type of esotropia and early utilization helped avoid the onset of amblyopia, monocular inhibition and abnormal retinal correspondence.

Adolescent↗
PubMed1993

A comparative clinical study on prevention and treatment with selected chronomedication of leukopenia induced by chemotherapy.

During the period of therapy, leukopenia induced by chemotherapy was less severe and was cured more rapidly in the selected chronomedication group (CMG) than in the routine medication group (RMG). The incidence of leukopenia was markedly lower in CMG (12.9%) than in RMG (48.4%), and the rate of uneventful completion of chemotherapy was also higher in CMG (96.8%) than in RMG. These results suggest that selected chronomedication may be beneficial to the successful completion of chemotherapy in patients with malignant tumor.

Adult↗
PubMed1993

[MRI diagnosis of mediastinal tumors: a report of 20 cases].

With the use of MRI, 20 pathologically proved cases of mediastinal tumor were analysed, of which 13 cases were also studied with CT. Compared with CT, the three-dimensional morphological study of the lesions by MRI provided better evaluation of their location and of their characteristics. The abnormal signals on T1WI, PDWI and T2WI images, particularly of lipoma, fluid-contained cyst, lymphoma and cystic teratoma, were highly accurate in diagnosing mediastinal tumors; in addition, MRI was ideal for demonstrating the tumor capsule in neurogenic tumor or fibrous septa within the lipoma. Specific MRI findings facilitate the diagnosis of an aneurysm. Finally, the limitations of MRI were also discussed.

Humans↗
PubMed1993

[Surgical treatment of A-pattern strabismus with over-acting superior oblique muscles].

13 cases of A-pattern strabismus with overacting superior oblique muscles were treated with Berke's procedure. Depending on the severity of superior oblique muscle overaction, simple tenotomy or partial tenectomy of the superior obliques was performed. For cases of A-pattern strabismus < 30 prism diopters, bilateral superior oblique muscle weakening might result in overcorrection, and for cases > 40 prism diopters, bilateral superior oblique weakening should be accompanied with vertical displacement of the horizontal muscles. For patients with stereoacuity of 40 arc seconds, surgery should be refrained from in order to avoid post-operative cyclodeviation.

Adolescent↗
PubMed1993

The effect of laminin on molecular motion in the cell membrane and on cell motility.

We have studied the variation of lateral diffusion of proteins in the cell membrane, of membrane lipid fluidity and of the electrophoretic motility (EPM) of macrophages after treatment with extrinsic laminin. The results showed that the lateral diffusion coefficient D value of membrane proteins, the fluidity of membrane lipids and the EPM of macrophages were decreased after laminin had bound to its membrane receptor on the macrophages. These results are important for developing an understanding of the early reaction of plasma membranes and cells in the presence of laminin.

Animals↗
PubMed1993

Clinical and experimental studies of JPYS in reducing side-effects of chemotherapy in late-stage gastric cancer.

This article reports a research project undertaken for more than 16 years by the Cancer Department of Guang An Men Hospital. Tonic Jian Pi Yi Shen (JPYS), which nourishes the spleen and kidney, was used in combination with chemotherapy in the treatment of late stage gastric cancer patients for the purpose of promoting completion of the chemotherapeutic course, improving the general condition, ameliorating the reaction in the digestive system, protecting hemopoiesis and strengthening immunocompetence. The results of lab experiments were found to coincide with those of clinical application.

Adenocarcinoma↗
PubMed1992

Energy metabolism in myocardial stunning.

We investigated the effect of reversible ischemia, leading to persistent contractile dysfunction (stunning), on myocardial energy metabolism. The balance of energy metabolism is expressed by the phosphorylation state of cytosolic nucleotides. This variable cannot be measured directly because of nucleotide compartmentation, but in the isolated heart it can be estimated by the release of purine catabolites. We have previously shown that increased energy consumption or impaired energy production cause purine release to increase, while primary reduction in energy consumption has the opposite effect. Isolated working rat hearts were reperfused after 10 min of global ischemia, measuring hemodynamic variables, tissue high energy phosphate compounds and purine release. In post-ischemic recovery, aortic flow and minute work decreased to 82 +/- 3% and 77 +/- 4% of control, adenine nucleotide pool was reduced by 4.6 mumol/g dry wt, phosphocreatine to creatine ratio increased significantly and purine release decreased to 42 +/- 6% (P < 0.01). The rate of purine salvage, as evaluated by the incorporation of exogenous 3H-adenosine and 14C-hypoxanthine into tissue nucleotides, was much lower than net purine release, and was unchanged after ischemia and reperfusion. The adenine nucleotide pool could be depleted to the same extent as in the stunned myocardium by prolonged (60 min) aerobic perfusion. In this group the hemodynamic variables were unchanged and purine release averaged 87 +/- 9% of control (P = NS). In other experiments prolonged perfusion was combined with preload reduction in order to decrease energy demand. This protocol reproduced the effects of ischemia-reperfusion: aortic flow and minute work averaged 79 +/- 4% and 73 +/- 9% of control, adenine nucleotide depletion was 4.4 mumol/g dry wt and purine release decreased to 38 +/- 5% (P < 0.01). Our findings support the view that stunning is not due to adenine nucleotide depletion or to impairment in energy production, which would cause purine release to increase, but rather to primary reduction in energy utilization.

Animals↗
PubMed1992

Effect of myristoylation on p27 nef subcellular distribution and suppression of HIV-LTR transcription.

The effect of myristoylation on p27nef subcellular distribution and suppression of HIV-1 transcription was examined by transfecting COS-7 cells with plasmids expressing either myristoylated (pSVnef) or nonmyristolyated p27nef (pSVnefala2). Similar levels of myristoylated and nonmyristoylated p27nef were expressed with only the product of the pSVnef plasmid being myristoylated. Immuno-histochemical microscopy and radioimmunoprecipitation revealed myristolyated p27nef only in the membrane fraction while nonmyristolyated p27nef was found distributed between the nucleus and the cytosol fractions. The effect of myristoylation on p27nef suppression of HIV LTR controlled transcription was examined in transient transfected COS cells and in CEM human T-cell clones consituitively expressing either myristolyated or nonmyristolyated p27nef by cotransfecting with a chloramphenicol acetyltransferase (CAT) plasmid under control of the HIV-1 LTR. In both systems, myristoylated p27nef exhibited a 13- to 18-fold inhibition of basal CAT activity while the nonmyristolyated mutant and the same plasmid carrying the nef gene in a reverse orientation inhibited CAT activity one- to two-fold. These results confirm the cytoplasmic membrane localization of p27nef and establish that its subcellular targeting is dependent on covalently attached myristate. The data also provide further evidence that p27nef acts as a transcriptional suppressor and establishes for the first time that myristolyation is required for the full manifestation of this effect.

Cell Line↗