Biomedical subjects

C Mao

Publications and source records attributed to C Mao.

138 records · Page 8Linked to original sources

PubMed1994

[Age-related differences of blood flow distribution in canine mandibular ramus].

Blood flow distributions of canine mandibular rami in two different age groups were measured using the radioactive microsphere technique. The blood flow rates (ml/min/100g) of six regions of canine mandibular ramus in the infant group were 20.26 +/- 3.45, 10.70 +/- 2.69, 6.52 +/- 2.59, 8.92 +/- 2.47, 14.19 +/- 3.33 and 12.05 +/- 3.07. The blood flow rates of the correspondent regions of mandibular ramus in the adult group were 12.02 +/- 2.31, 8.65 +/- 2.02, 4.39 +/- 1.47, 6.07 +/- 1.28, 7.44 +/- 1.70, and 5.49 +/- 1.42. The blood flow rates of six regions of mandibular ramus in the infant group were all significantly higher than that of the correspondent regions of the adult group. The distribution patterns of blood supply to mandibular ramus are also not identical between the infant and the adult groups. The age-related differences of blood flow distribution of canine mandibular ramus reflects the intimate relation between the blood supply and growth of mandibular ramus.

Age Factors↗

PubMed1994

Measurement of regional bone blood flow in the canine mandibular ramus using radiolabelled toad red blood cells.

Toad red blood cells were used to measure regional bone blood flow in the canine mandibular ramus. The blood cells were labelled with sodium pertechnetate and fixed in 10% formalin; they were 22 x 15 microns in size and had a specific gravity close to that of dog red blood cells. These cells had no discernible effect on systemic hemodynamics after injection, did not agglutinate, were well mixed and evenly distributed throughout the body, and were completely extracted in one circulation through the mandible. The mandibular ramus was divided into six regions, and the blood flow rates in each were found to be similar to those reported in previous studies with radiolabelled carbonized, microspheres. Furthermore, the blood flow distribution pattern of the mandibular ramus determined in this study was identical to that of our previous study using the bone-seeking radionuclide method. We suggest that radiolabelled toad red blood cells are an ideal marker for measuring regional blood flow in the canine mandible.

Animals↗

PubMed1993

Mutant human cells defective in induction of major histocompatibility complex class II genes by interferon gamma.

Using immunoselection, we have isolated 11 independent mutant HT1080 fibrosarcoma cell lines defective in the induction by interferon gamma (IFN-gamma) of the expression of the human leukocyte antigen HLA-DRA. The mutations are recessive and fall into five complementation groups. All the mutants are affected mainly in the expression of major histocompatibility complex class II and invariant-chain genes. Type I mutants (three complementation groups) are completely defective in induction of the invariant-chain and class II HLA-DP, -DQ, -DR, and -DM genes, whereas type II mutants (two complementation groups) induce these genes weakly in response to IFN-gamma, in the order DPB > DRA > invariant chain. The induction by IFN-gamma of the mRNAs for class I, TAP1, LMP7, and 9-27 is partially defective and the induction of the proteins IRF-1 and ICAM-1 is normal in both types of mutants. All the mutants respond normally to IFN-alpha. The mutants are stable and thus can be used to clone the affected genes by reversion.

Antibodies, Monoclonal↗

PubMed1992

Solitary true cyst of the pancreas in an adult.

A 35-yr-old woman was presented to the hospital because of nausea 20-30 min after eating, associated with weight loss. A CT scan revealed a cystic lesion in the neck of the pancreas. At operation, a 3-cm diameter cyst was excised from the pancreas. Endoscopic retrograde pancreatography (ERP) was used intraoperatively to identify the transected pancreatic duct, after which a Roux-Y pancreaticojejunostomy was performed. Histologically, the cyst proved to be unilocular and was lined with cuboidal epithelium. The natural history of this lesion is unknown as only four previous case reports of unilocular true cysts in adults have been reported in the English literature. These are reviewed.

Adult↗

PubMed1992

Pathogenic autoantibody-inducing gamma/delta T helper cells from patients with lupus nephritis express unusual T cell receptors.

In previous work, we found that only 59 (15%) of 396 "autoreactive" T cell clones derived from five patients with lupus nephritis had the ability to selectively augment the production of pathogenic anti-DNA autoantibodies and the majority (49/59) of those autoimmune T helper (Th) clones were CD4+. Surprisingly, 7 of those Th clones were CD4-/CD8- and gamma/delta TCR+, capable of augmenting the production of pathogenic anti-DNA autoantibodies up to 125-fold. The gamma/delta Th clones responded in a MHC-nonrestricted manner to some endogenous autoantigen associated with heat shock proteins (HSP60) on the lupus B cells. The gamma/delta TCR genes expressed by 4 of these Th clones were amplified and sequenced here. Three of the 4 Th clones, each from a different lupus patient, expressed a gene from the V gamma 1 subgroup. Moreover, 2 of the Th clones expressed V delta 5, and the others V delta 1 or V delta 3. These TCRs are rarely expressed by peripheral blood gamma/delta T cells of normal adult humans. The predominant gamma/delta T cells in human peripheral blood express V gamma 2 (V gamma 9) and V delta 2 TCR genes, including HSP-responsive T cells. None of the lupus Th clones expressed this combination of TCR genes. In addition, some of these pathogenic autoantibody-inducing Th clones from the lupus patients had limited diversity and few N-nucleotide additions in their gamma/delta TCR junctional regions (CDR3), thus resembling fetal gamma/delta thymocytes early in ontogeny.

Base Sequence↗

PubMed1990

Rapid increase of the human IFN-gamma receptor phosphorylation in response to human IFN-gamma and phorbol myristate acetate. Involvement of different serine/threonine kinases.

Various cell surface receptors are phosphorylated upon binding of their ligand, and this phosphorylation seems to be involved in the signal transduction or in the feedback regulation of this signal. The possibility of a phosphorylation of the human IFN-gamma receptor (hu-IFN-gamma-R) has been investigated with 32P-labeled whole Raji cells and receptor purification either by immunoprecipitation with an anti-hu-IFN-gamma-R polyclonal antiserum or by affinity chromatography. The hu-IFN-gamma-R was found to be phosphorylated at a basal level. Upon incubation of the cells with recombinant hu-IFN-gamma, a dose-dependent two-fold increase of this phosphorylation was observed. Phosphoamino acid analysis by TLC showed that the same amino acids, serine and threonine, are phosphorylated at a basal level and after incubation with hu-IFN-gamma. Protein kinase C and Ca2+/calmodulin-dependent kinase pathways have been reported in some cases to be involved in the signal transduction pathway of hu-IFN-gamma. Both pathways involved the activation of a serine/threonine kinase and therefore we have investigated the possibility of hu-IFN-gamma-R phosphorylation by these kinases. PMA, an activator of protein kinase C, induced a rapid increase of the receptor phosphorylation in Raji cells, whereas the Ca2+ ionophore A23187 did not. PMA-induced hu-IFN-gamma-R phosphorylation was not associated with any effect on expression or inactivation of the receptor. PMA alone did not mimic the hu-IFN-gamma effect in Raji cells as measured by induction of IP-10 gene expression, a high specific marker of hu-IFN-gamma response. But the protein kinase C inhibitors, 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine (H7) and staurosporine, reduced this IFN-gamma-induced expression. However, H7 and staurosporine treatment as well as protein kinase C depletion suppressed PMA-induced receptor phosphorylation, whereas constitutive and hu-IFN-gamma-induced phosphorylation remained unchanged. Our results suggest that the serine/threonine kinase involved in the hu-IFN-gamma-R phosphorylation induced by IFN-gamma is different from protein kinase C.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗

PubMed1990

Differential regulation of the human IFN-gamma receptor expression in Raji and IM9 lymphoblastoid cells versus THP-1 monocytic cells by IFN-gamma and phorbol myristate acetate.

Expression of the human (hu) IFN-gamma-R has been studied in Raji and IM9 cells (two B lymphoblastoid cell lines) and in THP-1 cells (a monocytic cell line) with respect to IFN-gamma binding sites, receptor protein and mRNA levels. Although, in these three cell lines, the hu-IFN-gamma-R mRNA was expressed to the same extent, the high affinity receptor was expressed differently both in cell surface receptor binding and amount of receptor protein. Various ligands are able to modulate the expression of their own receptor. We investigated the modulation of the hu-IFN-gamma-R by its ligand. Hu-IFN-gamma induced a rapid and dose-dependent decrease of its cell surface receptor number without alteration of receptor affinity, amounts of receptor protein or hu-IFN-gamma-R mRNA accumulation and stability. Thus, in Raji, IM9, and THP-1 cells, the hu-IFN-gamma had no effect on its receptor gene expression and the cell surface decrease was simply due to ligand blocking and receptor internalization rather than true down-regulation. The second messenger in the hu-IFN-gamma signal transduction pathway is not well characterized, but activation of protein kinase C has been reported in some cases. Therefore, the modulation of the hu-IFN-gamma-R expression by PMA, a potent activator of protein kinase C and a modulator of other receptor expression, has been investigated. In Raji and IM9 cells, PMA had no or few effects on the cell surface receptor number and no detectable effect on the receptor protein or on mRNA levels. In contrast, in THP-1 cells, PMA treatment induced a time and dose-dependent five- to sixfold increase of the cell surface receptors due to a rapid and persistent increase of the hu-IFN-gamma-R gene expression in THP-1 cells was specifically inhibited or reversed by hu-IFN-gamma treatment. The modulation of the hu-IFN-gamma-R expression by PMA in THP-1 cells and by hu-IFN-gamma in PMA-treated THP-1 cells seems associated with their effect on monocyte-macrophage differentiation and/or macrophage activation.

Blotting, Northern↗

PubMed1989

Molecular characterization of the human interferon-gamma receptor: analysis of polymorphism and glycosylation.

Different molecular masses have been assigned to the human interferon-gamma receptor (HuIFN-gamma-R) by several authors. After extensive purification from Raji cells, this receptor was shown in a previous work to consist of two major protein species with molecular masses of 92 kD and 50 kD, as revealed by SDS-PAGE. We show here that the 50-kD band is most probably a degradation product of the 92-kD band due to a trypsin-like protease active during the purification process. The native protein of Raji cells seems, therefore, to have a molecular mass of 92 kD. The same molecular mass was found with Colo 205 cells (derived from a colon carcinoma). However, in conditions where degradation does not occur, the HuIFN-gamma-R shows a certain polymorphism: in IM-9 cells, another B-cell line, two bands exist with molecular masses of 95 kD and 85 kD, and in Wish cells, an amnion-derived cell line, one (or two) band(s) can be detected around 87 kD. This polymorphism is due at least in part to a variable extent of N-glycosylation from line to line and also within the same line, since after tunicamycin treatment of the Raji, IM-9, and Wish cells, very similar bands are obtained with a molecular mass of 72 kD.

Blotting, Western↗

PubMed1988

The sperm penetration assay: can it discriminate between fertile and infertile men?

The sperm penetration assay with zona-free hamster ova is widely used to evaluate male infertility. Despite a growing body of literature about this assay, its results remain difficult to interpret. To evaluate the clinical usefulness of this test, we reviewed the world's literature about this assay and analyzed the test's performance. Its sensitivity ranges from 0.00 to 1.00 and specificity ranges from 0.95 to 1.00 for diagnosing male infertility. For predicting in vitro fertilization failures, its sensitivity varies from 0.00 to 0.78 and specificity ranges from 0.51 to 1.00. The reproducibility of this assay is not clear, and there is little standardization of methods between laboratories. Until the validity and reproducibility of the sperm penetration assay have been established, this expensive test should probably not be used to evaluate infertile couples.

Female↗

PubMed1988

A workshop on ethnic and cultural awareness for second-year students.

In 1984, 50 percent of the first-year students at the University of Southern California School of Medicine felt unprepared to handle the cultural barriers between themselves and their patients during their clinical rotations. Therefore, in 1985 a group of students developed a four-hour workshop designed to teach fellow students about ethnic and cultural issues in patient care. Since then the workshop, which uses videotaped vignettes, discussions, and role-playing exercises, has become a required part of the Introduction to Clinical Medicine course for all second-year students. Evaluation of the program in 1985 compared pretest and posttest questionnaires. The participants showed improvement in understanding several specific issues discussed during the workshop, but overall no significant differences were found. In 1986 and 1987, evaluations were based upon the students' attitudes about content, format effectiveness, and subject matter. They consistently responded favorably in all these areas.

Attitude of Health Personnel↗

PubMed1987

Contrast visual testing in neurovisual diagnosis.

Contrast visual testing (CVT) is a psychophysical visual test of undetermined diagnostic capability in many neurovisual disorders. CVT of 32 controls and 39 patients was compared with the pattern visual evoked response (PVER) from each group. CVT was more sensitive than PVER in detecting visual dysfunction in pseudotumor cerebri and subclinical optic neuritis and showed potential in distinguishing papilledema from pseudopapilledema. PVER was more sensitive than CVT in detecting subclinical visual dysfunction in MS and optic nerve compression. Neither was abnormal in asymptomatic Leber's optic neuropathy. In nonorganic visual loss, CVT data were variable and inconsistent, supporting this diagnosis; PVER was consistently normal. Although in certain disease conditions, each detected subclinical visual dysfunction, neither CVT nor PVER provided specific information leading to an etiologic diagnosis.

Adolescent↗

PubMedDate not supplied

Adsorption of gamma-aminobutyric acid to phosphatidylserine membranes.

The interaction of the negatively-charged phosphatidylserine (PS) and gamma-Aminobutyric acid (GABA) is examined in black lipid membranes (BLM) and inverse micelles. GABA does not permeate through PS membranes and, in concentrations of 10(-5)-10(-4) M, it reduces the negative potential at the membrane-aqueous solution interface. The effect is owing to the adsorption of the GABA cationic species and the consequent decrease of the negative surface charge density of the membrane. When the intrinsic pH of the membrane-solution interface is considered, the Gouy-Chapman-Stern theory describes the GABA screening effect and makes it possible to calculate the GABA-PS binding constant. This value is compared with that obtained measuring the partition of 14C-GABA between an organic phase containing PS and the aqueous solution. The results presented strongly suggest that the electrostatic force plays a major role in GABA-PS interaction.

Adsorption↗