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M Bai

Publications and source records attributed to M Bai.

85 records · Page 5Linked to original sources
PubMed1992

Affinity labeling of vertebrate oxidosqualene cyclases with a tritiated suicide substrate.

Pig and rat liver oxidosqualene cyclase (OSC) enzymes were purified to homogeneity and showed single bands on SDS-polyacrylamide gel electrophoresis with molecular masses of 75 kDa (pig) and 78 kDa (rat). Pig liver OSC was purified for the first time (441-fold with a yield of 39%). Chemical affinity labeling of pure or crude preparations of the liver cyclases using the mechanism-based irreversible inhibitor of OSC, [3H]29-methylidene-2,3-oxidosqualene ([3H]29-MOS), showed a single radioactive band at 75 kDa (pig) and 78 kDa (rat). Affinity labeling experiments were also performed with dog and human microsomal preparations and with yeast and plant cyclases. All of the vertebrate OSC enzymes were specifically labeled with [3H]29-MOS and gave a single band with molecular masses ranging from 70 to 80 kDa (rat, 78 kDa; dog, 73 kDa; pig, 75 kDa; and human, 73 kDa). In contrast, yeast lanosterol cyclase and plant cycloartenol cyclase were not labeled, demonstrating subtle differences in the active sites of animal, plant, and fungal enzymes.

Affinity Labels↗
PubMed1992

Epoxidation of 2,3-oxidosqualene to 2,3;22,23-squalene dioxide by squalene epoxidase.

Partially purified squalene epoxidase (SE) from pig liver converts 2,3-oxidosqualene (SO) to 2,3;22,23-squalene dioxide (SDO) with approximately one-half the efficiency of the epoxidation of squalene at pH 7.4. The SO to SDO conversion is independent of pH and shows an absolute requirement for exogenous FAD. Two noncompetitive SE inhibitors show selectivity in blocking squalene (Sq) to SO versus SO to SDO epoxidations. Finally, SDO inhibits the activity of crude pig liver oxidosqualene cyclase (OSC) with an IC50 of 16 microM. Thus, SE inhibitors not only reduce the production of SO from Sq, but also strongly suppress "leakage" of SO to the potentially harmful SDO in vitro.

Animals↗
PubMed1992

Inhibition and activation of porcine squalene epoxidase.

Pig liver squalene epoxidase (SE) has been partially purified from solubilized microsomes by DEAE-Sephacel and Blue Sepharose 4B chromatography. This stable and reproducible preparation was used to investigate the mechanism of several substrate-like inhibitors of SE and to study the effects of pH, metals, detergents, and cofactors on enzyme activity. Most divalent (1 mM) and trivalent (0.1 mM) metal cations had little effect on SE at pH 7.4; only ferrous and cupric ions showed ca. 50% reduction in SE activity. Interestingly, at pH 8.8, EDTA (10 mM) shows 1.8-fold enhancement of enzyme activity. Among the detergents, Triton X-100 was clearly superior for solubilization and purification of porcine SE; Tween 80, Lubrol-PX, 3-[(3-cholamidopropyl)dimethylammonio]propanesulfonic acid, octyl beta-glucoside, and three different Zwittergents were much less effective for SE solubilization. Partially purified pig liver SE showed maximal activity at pH 8.8-9.0. Trisnorsqualene alcohol and trisnorsqualene cyclopropylamine were noncompetitive inhibitors at pH 8.8, with Ki values of 4 microM and 180 nM, respectively; these two inhibitors were not substrates for SE. In contrast, 26-hydroxysqualene was both a competitive inhibitor with a Ki value of 4 microM at pH 8.8 and a substrate for SE. An unexpected enhancement (up to 350%) of SE activity was observed at pH 7.4 following preincubation with selected nonpolar derivatives of farnesol and farnesoic acid. At pH 8.8, this effect was less dramatic but still evident.

Animals↗
PubMed1992

[Cutaneous melanoma of the cervicofacial region. Personal experiences].

The malignant melanomas are expansive tumors of neoplastic melanocytes. In the present study, five cases of patients are reported which have been hospitalized in E.N.T. department of our hospital during the last four years with skin melanomas of the head and neck. We note our opinions on diagnosis and treatment of these malignant tumors.

Adult↗
PubMed1992

[Inverted papilloma of the nose. Apropos of a case associating polyps and an inverted papilloma of the nose].

In this article is presented a case report of a 59 years old woman with a medical history of recurrent nasal polyps (from 20 years ago). This woman presented an inverted papilloma in the middle meatus of the lateral wall of the nasal cavity simultaneously with the nasal polyps, and she was faced with surgical intranasal removal. The patient, two years later, presented again nasal polyps, but without any indication of the recurrence of the inverted papilloma. It is noticed the value of the local surgical removal of the inverted papilloma in patients who do not present extensive tumors.

Female↗
PubMedDate not supplied

Tissue distribution and metabolism of gamma-linolenoyl-3-eicosapentaenoyl propane diol enterally or intravenously administered to mice bearing human pancreatic carcinomas.

Synthetic propane diol lipids have been proposed as novel compounds to deliver cytocidal polyunsaturated fatty acids (PUFA) such as gamma-linolenic (GLA) and eicosapentaenoic (EPA) acids. To assess the biodistribution and metabolism of these PUFA in immunodeficient mice bearing human pancreatic carcinomas (AsPC-1), gamma-linolenoyl-3-eicosapentaenoyl propane diol (GE diol) was provided in a fat-free diet (5% w:w) for 6 weeks or parentally administered as 14C-GE diol (1 or 3 consecutive doses of 1.66 g/kg/day) in an innovative non-ionic-digalactosyldiacylglycerol emulsion. In tumor, liver, brain, kidney, plasma and fat tissue of mice fed GE diol, PUFA were increased over 25-fold, except for arachidonic acid (AA) levels, which were reduced or remained constant when compared to mice fed control corn oil diet. GLA and EPA were mainly stored in fat tissue. The recovery of radioactivity from the i.v. infected 14C-GE diol was dose and time dependent. Ten days after the i.v. infusion, GLA was only detected in substantial concentrations in tumor and in fat tissue (21 and 202 micrograms/g, respectively). Overall, these studies showed that: GE diol emulsions provide 640-fold higher doses of both GLA and EPA without causing hemolysis or adverse effects in the host mouse when compared to free PUFA infusions; GE diol is metabolized after oral or i.v. administration; tumor concentrations of GLA and EPA from the enterally administered diol were 4 to 13-fold higher than the in vitro cytotoxic levels; EPA, competes with AA and probably inhibits the activity of delta 5 desaturase without affecting the elongation of GLA in the host and tumor tissue; the change in PUFA profile modifies the substrates for eicosanoid synthesis. In short, a potentially desirable cytotoxic PUFA pattern can be achieved in host tissues and, in particular, in a human pancreatic tumor by providing GLA and EPA in the form GE-diol. These findings guarantee further investigations in oncology with this neutral diol lipid.

Adipose Tissue↗
PubMedDate not supplied

Immunohistochemical expression of the p53, p21/Waf-1, Rb, p16 and Ki67 proteins in multiple myeloma.

The aim of this study was to investigate the immunohistochemical expression of the proteins p53, Waf-l/p21, Rb, p16 and Ki67 in 38 cases of multiple myelomas (MM) and 4 cases of solitary extramedullary plasmacytomas in relation to the tumor histological grade and stage. In bone marrow (BM) biopsies from MM, overexpression of p53 and p21 proteins, in comparison to plasma cell infiltrates in non-pathological bone marrow, was detected in 13 out of 38 and 21 out of 38 cases, respectively. The combined immunoexpression of p53 and p21 proteins in the 38 cases of MM showed the following patterns: a) p53+/p21+ (13 cases) b) p53-/p21+ (8 cases) and c) p53-/p21- (17 cases). Rb, p16 and Ki67 proteins were detected in tumor cells in all 38 cases and their expression increased proportionally to tumor grade. The 4 cases of solitary extramedullary plasmacytomas showed the p53+/p21+ pattern in 2 cases and the p53-/p21+ pattern in 2 cases, all of them displaying Rb, p16 and Ki67 expression in tumor cells. The pattern p53+/p21+ might represent cases with wild-type p53 able to induce p21 expression. However, in previous studies p53 mutations were reported in about 3-10% of MM, and they were strongly associated with advanced disease. Thus, in some p53+/p21+ cases associated with high p53 expression and advanced disease, p53 gene cannot be excluded and up-regulation of p21 expression may be p53- independent. P53 overexpression correlated with increased tumor grade (p < 0.005), advanced histological stage (p < 0.001) and Ki67 expression in more than 10% of tumor cells (p < 0.001). Since increase in Ki67 expression also correlated with increased tumor grade (p < 0.001) and advanced histological stage (p < 0.001), these findings suggest that impairment of the p53 growth control pathway is associated with tumor progression in MM. Thus, p53 and Ki67 immunostaining in routine BM biopsies may be helpful for the detection of MM with potentially aggressive behavior. Overexpression of p21 in MM correlated with higher Ki67 expression (p < 0.005), suggesting that the p21 function of arresting cell-cycle is impaired. Ki-67 expression in MM increased in parallel with p16 (p < 0.001) and Rb expression (p < 0.001). Rb expression could represent a growth control response which, however, might not be able to induce growth arrest in view of the parallel increase in Ki67 expression and of previous findings showing that Rb protein in MM cells is expressed mostly in its phosphorylated form.

Cyclin-Dependent Kinase Inhibitor p16↗
PubMedDate not supplied

FHIT gene expression in human urinary bladder transitional cell carcinomas.

BACKGROUND: Our purpose was to investigate the expression of FHIT (Fragile Histidine Triad) gene product in a series of 110 urinary bladder TCCs, and its eventual relationship with histological grade, clinical stage, recurrences and patients' survival. MATERIALS AND METHODS: We performed immunohistochemistry in archival material of formalin-fixed, paraffin-embedded tissues, using the anti-Fhit antibody and the Streptavidin-biotin peroxidase method. RESULTS: In 30 out of 110 cases (27.27%) Fhit protein was absent whereas in 32 cases (29.08%) it was abnormally expressed. In 48 cases (43.63%) Fhit protein was diffusely expressed in all tumor cells. A statistically highly significant correlation (p < 0.001) was noticed between Fhit protein absence or reduction and clinically advanced tumors. Conversely, abnormal Fhit protein expression was not associated with age, histological grade, tumor size, number of recurrences, and clinical outcome in terms of patients' survival. CONCLUSIONS: These results confirm that FHIT gene inactivation is a late event in urinary bladder carcinogenesis. Fhit protein reduced expression or complete absence correlates with advanced clinical stage of the disease, and does not seem to correlate with tumor recurrences and patient survival.

Acid Anhydride Hydrolases↗
PubMedDate not supplied

Monoclonal immunoglobulins and autoantibodies in lymphoid malignancies.

The presence of serum monoclonal or oligoclonal immunoglobulins (paraproteins) was investigated in 38 non-Hodgkin's lymphoma and chronic lymphocytic leukemia patients, 33 patients with solid tumors and 33 healthy individuals. Seventy two percent of non-Hodgkin's lymphoma and 31% of chronic lymphocytic leukemia patients had serum paraproteins, in contrast to 21% and 15% of solid tumor patients and normal controls respectively. There was no significant prevalence of a certain isotype or light chain in the non-Hodgkin's lymphoma, chronic lymphocytic leukemia and solid tumor groups. In the healthy individuals all bands were monoclonal of the IgG isotype. No correlation was found between histologic grading of lymphoid malignancy or disease stage and serum monoclonality. No serologic or histologic autoimmune features were demonstrated in non-Hodgkin's lymphoma and chronic lymphocytic leukemia patients. In addition, no correlation was found between serum autoantibody activity and mono- or oligoclonal immunoglobulins.

Aged↗
PubMedDate not supplied

Overexpression of C-myc, Ras and C-erbB-2 oncoproteins in carcinoma of unknown primary origin.

The role of oncogenes in carcinoma of unknown primary site (CUP) has not yet been elucidated. In the present study the expression of the c-myc p62, ras p21 and c-erB-2 p185 oncoproteins were studied by a 3-step immunoperoxidase technique in 26 cases of CUP. Positive immunoreactivity was observed in 96% of the cases for c-myc, 92% for ras and in 65% for c-erb-2, with at least half of tumor cells labelled in 85%, 92% and 58% respectively. The degree of staining intensity was considered moderate or strong in more than half of the cases for all oncogene products. In conclusion, our results showed that patients with CUP have an extremely high overexpression of all three oncogenes studied. Nevertheless, the biological role of these overexpressed oncoproteins, their relationship with different histological or clinical parameters and their diagnostic or prognostic value need further evaluation.

Adenocarcinoma↗