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Biomedical subjects

B Yu

Publications and source records attributed to B Yu.

At least 163 records · Page 9Linked to original sources
PubMed1995

Signal transduction pathways leading to arachidonic acid release from neutrophilic HL-60 cells. The involvement of G protein, protein kinase C and phospholipase A2.

Arachidonic acid release from undifferentiated and neutrophilic HL-60 cells was studied. In neutrophilic cells it was stimulated by N-formyl-Met-Leu-Phe and mastoparan by a mechanism involving Gi protein and phospholipase C and was largely dependent on diacyglycerol lipase. Maximum release from both cell types was achieved with fluoride and required cellular energy. Inhibitor studies suggest that arachidonic acid release by fluoride stimulation leads to phospholipase A2 activation with signal transduction involving phospholipase C and protein kinase C. Only neutrophilic cells responded to phorbol ester if Ca(2+)-ionophore was simultaneously present but this effect was abolished by extended treatment with phorbol ester. Thus, protein kinase C plays a major role in highly stimulated neutrophilic cells. These cells are differently equipped with protein kinase C isoenzymes compared with undifferentiated cells. In contrast, both cell types contain similar levels of type II and cytosolic phospholipases A2, the former being by far the more prevalent.

Arachidonic Acid↗
PubMed1995

Critical characteristics of technique in throwing the discus.

The purpose of this study was to identify those characteristics of the techniques used by elite discus throwers that are most closely related to the distances they record. The subjects were the competitors in the discus throw events at two major meetings. Two S-VHS video cameras were used to record the performances of the subjects; the direct linear transformation (DLT) procedure was used to obtain three-dimensional data from these records. For the males, the change in speed of the discus during the second double support phase was more influential than the change in speed during any other phase in accounting for differences in the distances of the throws recorded. For the females, the changes in speed during the flight phase and during the second double support phase were about equally influential in accounting for differences in the distance thrown. The findings suggest that emphasis placed on achieving a large change in the speed of the discus during the second double support phase is well founded; that the speed of release is the most influential determinant of the distance of the throw; and that, in most cases, the aerodynamic forces exerted on the discus during the flight increase the distance of the throw.

Acceleration↗
PubMed1995

Carbapenem antibiotic production in Erwinia carotovora is regulated by CarR, a homologue of the LuxR transcriptional activator.

Strain GS101 of Erwinia carotovora makes the carbapenem antibiotic, 1-carbapen-2-em-3-carboxylic acid. Mutants defective in antibiotic production can be assigned to two groups, group 1 and group 2. Group 2 mutants are defective in the carl gene encoding a protein responsible for synthesis of the Lux autoinducer N-(3-oxohexanoyl)-L-homoserine lactone (OHHL), which is required to induce carbapenem synthesis in strain GS101. In this paper we describe the molecular genetic analysis of the group 1 mutants which we presumed were defective in the carbapenem biosynthesis (car) genes. We isolated a cosmid (cWU142) that complemented the group 1 mutants of strain GS101. A small (1.03 kb) subclone of cWU142 complemented most of the group 1 mutants, and the sequence revealed that the relevant gene (carR) encodes a homologue of the Vibrio fischeri LuxR protein. A disproportionately high frequency of carR mutants arose in strain GS101 and this was due to carR acting as a 'hot spot' target for secondary transposition of a Tn5 element in this strain. The CarR protein joins a rapidly growing list of homologues, found in taxonomically unrelated bacteria, which act as positive transcriptional activators of genes encoding diverse metabolic functions, including bioluminescence, exoenzyme virulence factor synthesis, cell division, plasmid conjugation, rhizosphere-specific gene induction, surfactant synthesis and antibiotic production. Most of these LuxR-type regulators have been shown to depend, for their function, on N-acyl homoserine lactones, which act as chemical signals enabling co-ordination of gene expression with cell density.

Amino Acid Sequence↗
PubMed1995

[Surgical treatment of carcinoma of low rectum].

1230 cases of low rectal cancer were treated surgically from 1954 through 1990 with a resectability rate of 79.92% and a curative resectability rate of 63.98%. Among curative resections, abdomino-perineal excision accounted for 71.16% and sphincter-saving resection for 28.84%. Before 1980, 19.19% cases were treated with SSR and since 1980 it was raisen to 41.04%. In comparison of the results of group before 1980 with those since 1980, the mortality rate of curative resection was 1.56% and 0.99% respectively. The 5-year survival rate of curative resection (life table method) was 58.96% +/- 2.87% in APR and 80.39% +/- 5.06% in SSR before 1980, and 71.65% +/- 3.28% in APR and 83.82% +/- 3.46% since 1980. The local recurrence after curative resection was 13.57% in APR and 12.33% in SSR. The data showed that in properly selected cases, the outcome was better in SSR than in APR either in survival or in quality of life. The feasibility and reasonality of the SSR and the rules for selecting the operative procedures in low rectal cancer were discussed in detail.

Female↗
PubMed1995

[Interference of selenium germanium and calcium in carcinogenesis of colon cancer].

We studied DMH induced colon cancer in 120 wistar rats, which were divided into 8 groups based on different diets. They were killed and autopsied on 4 weeks after the last injection of DMH. The tumors in various organs including its characteristics, number, site, histological types and ultrastructural changes were observed. The results showed that high fat diet has a significant effect on DMH induced colon cancer. Selenium and calcium can inhibit the effect of DMH and decrease the incidence of colon cancer. Selenium can also interfere the effect of high fat diet but germanium has no effect on colon carcinogenesis.

Animals↗
PubMed1995

LPS-dependent interaction of Mac-2-binding protein with immobilized CD14.

CD14 is a glycosylphosphatidyl-inositol (GPI)-linked, 55 kDa protein that binds bacterial lipopolysaccharide (LPS, endotoxin) and plays a key role in mediating cellular responses to this potent inflammatory stimulus. Binding of LPS to CD14 is facilitated by serum proteins such as LPS binding protein (LBP). To determine if there are additional plasma proteins that bind to CD14, plasma was passed over immobilized CD14 in the presence or absence of LPS, and retained proteins were eluted. This procedure isolated not only LBP but also a serum protein known as Mac-2-binding protein (Mac-2-BP), a 97 kDa species without a known function. Binding of both LBP and Mac-2-BP to CD14 required the simultaneous presence of LPS. Experiments with purified Mac-2-BP showed that this protein alone neither enabled responses of CD14-bearing cells to LPS nor blocked the ability of plasma to enable responses of CD14-bearing cells to LPS. However, Mac-2-BP did slow the neutralization of LPS mediated by plasma lipoprotein. These studies describe the first potential function for Mac-2-BP, and suggest that neutralization of LPS in plasma may be controlled by proteins in addition to LBP and CD14.

Acute-Phase Proteins↗
PubMed1995

[Changes in cytosolic free calcium and thromboxane B2 synthesis in platelets from diabetic subjects].

Using fura-2, a fluorescence indicator, we evaluated the changes of platelet cytosolic free calcium concentration ([Ca2+]i) and its role in regulation of thromboxane B2 (TXB2) synthesis in patients with diabetes mellitus (DM group, n = 27) and in healthy subjects (control group, n = 15). The A23187-evoked elevation of [Ca2+]i and TXB2 production were higher in the DM group than in the control group (P < 0.01 respectively). The rise in [Ca2+]i was correlated positively with TXB2 production. In contrast, stimulation with arachidonic acid, TXB2 production was unaltered between the groups, although arachidonate-induced [Ca2+]i was higher in the DM group than in the control group (P < 0.05). The results suggested that changes in platelets [Ca2+]i in diabetic subjects may contribute to increase in TXB2 synthesis, involved libration of free arachidonate from membrance phospholipids by the action of phospholipases. Since no significant difference was found between the diabetic patients with microangiopathy (n = 13) and without microangiopathy (n = 14), the results above may be involved in the development of diabetic microangiopathy.

Biological Transport, Active↗
PubMed1995

[The significance of p53 gene mutations and expressions in human colorectal tumors].

Using a polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) approach we analyzed 18 human colorectal adenocarcinomas for mutations in exons 5, 6, 7, 8 of p53 gene. At the same time, p53 gene product expression was studied immunohistochemically in these 18 cases in frozen sections. The expression of p53 protein was also immunohistochemically studied in formalin-fixed paraffin embedded specimens of 76 colorectal adenocarcinomas and 112 colorectal polyps. Eight out of 18 cases (44%) tested showed a variant band indicative of a mutation in exons 5-6 of p53 gene. Seven out of 8 cases (88%) with p53 gene mutations were positively stained for p53. There was no significant correlation between p53 expression and clinicopathological manifestations and prognosis. But the strongest staining was encountered in those cases with well differentiated and early stages of adenocarcinomas, while weaker staining was encountered in poorly differentiated and mucoid adenocarcinomas. p53 expression was not observed in proliferative polyps and adenomas with low grade dysplasia. The frequency of p53 expression reached 88% (P < 0.001) when adenoma showed malignant change. Among three types of adenomas, p53 expression was most frequent in villous type (P < 0.05). The frequency of p53 expression in adenoma, adenoma with malignant change and adenocarcinoma was 4%, 88% and 51% respectively. These indicate that genetic changes of p53 gene play an important role in the transformation from benign adenoma to adenocarcinoma. p53 immunohistochemistry can be used as a surrogate marker for p53 gene mutation for early discovery of colorectal adenocarcinomas.

Adenocarcinoma↗
PubMed1995

[Enhancement of gut absorptive function by early enteral feeding enriched with L-glutamine in severe burned miniswines].

14 miniswines (with multiple catheterization and 30% TBSA full thickness burns) were randomly and equally divided into N-Gln group and GLN group. Animals of GLN group were supplied with L-glutamine by 0.64%/kg.d and N-GLN group received equal amount of non-glutamine amino acids. Portal venous blood flow and gut absorptions of glucose, amino acids as well as fat were determined on PBD (post burn day) 1, 4, 7 and 10. The results indicated that the gut absorption obviously decreased in both group on PBD1, but the absorption of glucose and amino acids were much higher in Gln group than that of N-Gln group (P < 0.01). The absorptions of glucose, fat amino acids quickly increased in Gln group from PBD4, and tended to reach the preburn level on PBD7 and PBD10, meanwhile N-Gln group exhibited a slow increase of gut absorption. The absorptions of glucose, fat and amino acids were obviously lower than those of preburn on PBD7 and PBD10 (P < 0.01). This result suggests that oral feeding of glutamine improves efficiently the gut absorptive function after severe burns.

Amino Acids↗
PubMed1994

Effects of metformin on glucose and glucagon regulated gluconeogenesis in cultured normal and diabetic hepatocytes.

The effects of glucose and glucagon on the anti-gluconeogenic action of metformin were investigated in normal and diabetic hepatocytes. Glucose production from lactate was elevated by 88% in hepatocytes from fasted normal rats compared with hepatocytes from fed animals. Diabetes caused 3.5- and 2.1-fold increases in hepatic gluconeogenesis under fasting and fed conditions, respectively. Metformin (250 microM) suppressed glucose production by 37% in normal and by 30% in diabetic hepatocytes from fed rats. This drug was more effective (up to 67%) with increasing concentrations of glucose in the medium. Potentiation by metformin of insulin action on gluconeogenesis was elevated significantly (P < 0.01 to 0.001) by glucose in vitro. Metformin (75-250 microM) also counteracted the effects of glucagon at optimal concentrations in normal (32-68%) as well as diabetic (8-46%) hepatocytes. The findings of this study indicate that (i) the anti-gluconeogenic effect of metformin is enhanced by glucose in vivo and in vitro; and (ii) the suppression of glucagon-induced gluconeogenesis by metformin could play a role in its glucose-lowering effects in diabetic conditions.

Animals↗
PubMed1994

Dissociation and reassociation of the bovine pituitary multicatalytic proteinase complex.

The eukaryotic multicatalytic proteinase complex (proteasome) is a high molecular mass enzyme which contains 13-15 nonidentical subunits of similar size (molecular masses of 21-31 kDa), but differing widely in net charge (isoelectric points ranging from 3 to 10). At least four catalytic components termed chymotrypsin-like, trypsin-like, peptidylglutamyl peptide-hydrolyzing, and caseinolytic are associated with the proteinase. The catalytic nature of the components is unknown, since sequences of cloned subunits bear no homology to known proteinases and proteolytically active subunits have not been isolated. Analysis of the relationship between structure and catalytic function would be greatly facilitated if a means for reversibly dissociating and reassociating the proteinase were available. We provide the first evidence of reassembly of dissociated multicatalytic proteinase complex into a functional molecule. Incubation with the organic mercurial, p-chloromercuribenzoic acid disrupts in a concentration-dependent manner the quaternary structure of the enzyme, leading to formation of a heterogeneous population of subunits. Dissociation of the complex coincides with progressive loss of chymotrypsin-like, trypsin-like, and peptidylglutamyl peptide hydrolyzing activities. The caseinolytic activity of the residual undissociated enzyme is markedly activated. Exposure of the dissociated enzyme to dithiothreitol restores the catalytic profile and reassociates the enzyme. Evidence for catalytically active subcomplexes was not obtained indicating that structural integrity may be necessary for expression of all defined activities.

Amino Acid Sequence↗
PubMed1994

Insulin-like effects of sodium orthovanadate on diacylglycerol-protein kinase C signaling in BC3H-1 myocytes.

In this paper we examine whether sodium orthovanadate activates diacylglycerol (DAG)/protein kinase C (PKC) signaling systems that are activated by insulin in BC3H-1 myocytes. Like insulin, sodium orthovanadate provoked increases in membrane DAG, PKC enzyme activity, and immunoreactive PKC-beta. Concomitantly, both PKC enzyme activity and immunoreactive PKC-beta decreased in the cytosol, suggesting that sodium orthovanadate, like insulin, stimulated the translocation of PKC-beta from the cytosol to the membrane fraction. Sodium orthovanadate was also found to activate phospholipid signaling pathways that were previously reported to be activated by insulin, viz., inositol-lipid synthesis/turnover; phosphatidylcholine hydrolysis; and de novo phospholipid synthesis by activation of glycerol-3-PO4 acyltransferase. Our findings suggest that vanadate mimics insulin in the activation of specific phospholipid/DAG/PKC signaling pathways.

Animals↗
PubMed1994

A unique murine CD43 epitope Lp-3: distinct distribution from another CD43 epitope S7.

In foregoing studies, we found a unique B cell differentiation antigen Lp-3 which is expressed on pre-B and premature B cells in the bone marrow, but is negative on bone marrow mature B cells and peripheral resting B cells. Nonetheless, Lp-3 was clearly positive on the majority of CD5 B(B1) cells. When we examined the biochemical nature and partial amino acid sequences of purified 132-kDa Lp-3 molecules and the nucleotide sequence of the cDNA clones, we found that Lp-3 is an epitope of CD43. Thus, the monoclonal antibody (mAb) Lp-3 may be the first mAb to murine CD43 defined by primary target structure analysis. Comparison of tissue distribution of Lp-3 and S7, an epitope previously suggested to associate with murine CD43, showed that they were similarly distributed on thymocytes, peripheral B and T cells, granulocytes, and platelets. In the bone marrow, while both Lp-3 and S7 were negative on mature B cells, the former was positive on all B lineage cells at an early ontogeny and the latter was positive only on the minor population of pre-B cells and pro-B cells. Lp-3 and S7 epitopes also showed different distributions on basement membranes of renal glomerulus, bronchus, and endometrium, lining cells of choroid plexus and muscular cells of arterioles in a variety of tissues. As CD43 has various isoforms generated by different degrees of glycosylation of the common core peptide, it is likely that Lp-3 and S7 are associated with different CD43 isoforms.

Amino Acid Sequence↗
PubMed1994

Effect of different components of dietary fiber on the intestinal morphology of domestic rabbits.

A trial was conducted to study the effect of dietary fiber components (cellulose, pectin, lignin and alfalfa) on the performance and the intestinal structure of domestic rabbits. Different fiber components influenced villus height and muscle layer thickness of the jejunum and colon, and affected the crypt depth of the duodenum and ileum. A scanning electron microscope photograph showed a significant damage of the villi surface in the duodenum and jejunum by lignin supplementation; it also showed a significant damage in the cecal mucosa by cellulose, pectin and alfalfa supplementation.

Animals↗
PubMed1994

IgA nephropathy in three successive renal allografts: presumed recurrence of original disease.

We report a patient with presumed recurrence of IgA nephropathy in three successive cadaver transplants. Failure to recognize the cause of progressive renal failure in the first two transplants may have been associated with less than optimal treatment for his hypertension and nephrotic syndrome. His course illustrates the importance of biopsy-documented diagnosis of progressive dysfunction in kidney transplants.

Adult↗