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M Guo

Publications and source records attributed to M Guo.

At least 145 records · Page 8Linked to original sources
PubMed1992

[Cation channels formed in lipid bilayer by Pinellia ternata lectin].

Pinellia ternata lectin (PTL), a protein exhibiting hemagglutination activity and carbohydrate binding specificity to mannan was purified from rhizome of Pinellia ternata. In this work the actions of PTL on artificial lipid bilayer were investigated by means of the two-compartment system of Mueller and Rudin. The lipid bilayer with resistance more than 10G omega was formed by a solution of lecithin and cholesterol (20 mg/ml and 5 mg/ml respectively) in N-decane. The electrical properties of the lipid bilayer were investigated in voltage clamp mode. Several minutes after the addition of PTL (2 micrograms/ml) in one compartment the channel-like noise as well as a decrease of the resistance of the bilayer were observed. These actions were inhibited by mannan significantly. The resistance increase of the bilayer with PTL-channels could be observed from 2G omega to control level (greater than or equal to 10 G omega) immediately after addition of 40 micrograms/ml mannan. The discrete conduction steps were recorded at low concentration of PTL and at low holding potential. The predominant unit conductance was 35pS in symmetric KCl solution of 100 mmol/L. The selectivity of PTL-channel was estimated from Goldman-Hodgkin-Katz equation by measurement of the reversal potential in an asymmetrical salt solution. The results showed that PTL-channels were cation selective.

Cations↗
PubMed1991

Altered processing of integrin receptors during keratinocyte activation.

We used monoclonal antibodies against specific integrin subunits to examine the role of integrin receptors in keratinocyte activation. We found that before activation, beta 1 subunits in keratinocytes showed a diffuse distribution, whereas after activation, keratinocytes organized beta 1 receptors into marginal adhesion plaques. In immunoprecipitation experiments with antibodies against beta 1 integrin subunits, we found mostly immature subunits synthesized in keratinocytes freshly harvested from skin. Moreover, integrin receptor complexes immunoprecipitated from these cells by monoclonal antibodies against alpha 2, alpha 3, or alpha 5 subunits contained only immature beta 1 subunits. With keratinocytes cultured 4-7 days, anti-beta 1 antibodies immunoprecipitated mostly mature beta 1 subunits, and integrin complexes immunoprecipitated from cultured cells by anti-alpha subunit antibodies contained mostly mature beta 1 subunits. Antibodies directed against beta 1 subunits also inhibited keratinocyte migration. Based on these results, we suggest that up-regulation of migration by activated keratinocytes depends on changes in processing of pre-beta 1 subunits to mature beta 1 subunits. We also studied the distribution of integrin subunits in skin and on keratinocytes migrating out of skin explants. Whereas beta 1, alpha 2, and alpha 3 subunits were detected in keratinocytes in skin and migrating out of explants, alpha 5 subunits were observed only in migrating cells.

Cell Differentiation↗
PubMed1990

Activation of human keratinocyte migration on type I collagen and fibronectin.

The purpose of our studies was to learn more about the regulation of keratinocyte migration. Human keratinocytes freshly harvested from skin were relatively immotile cells, whereas keratinocytes harvested from cell culture migrated on type I collagen or fibronectin as measured in a phagokinesis assay. Development of migratory competence by keratinocytes varied depending on the culture substratum. Cells cultured on plastic were activated more quickly and to a greater extent than cells cultured on dermis. The effect of the culture substratum on migratory competence was reversible. That is, cells cultured on plastic showed reduced activity after subculture on dermis. Cells cultured on dermis showed increased activity after subculture on plastic. Freshly isolated as well as cultured keratinocytes contained beta 1 integrin subunits, but only cultured cells were able to organize the subunits into focal adhesions. These adhesion sites also contained vinculin. In epidermal explants, beta 1 integrin subunits were mostly in basal cells, often more prominent between lateral cell borders than at the epidermal-dermal interface. In keratinocytes that migrated out of skin explants, there appeared to be an increase in the intensity of beta 1 integrin subunit immunostaining, possibly because of the change in shape of migrating cells. Also, beta 1 integrin subunits were found around and beneath migrating keratinocytes. These results show that changes in the distribution of beta 1 integrin subunits accompany development of migratory competence.

Cell Adhesion↗
PubMed1990

[Correlation function and power spectrum analysis of auditory brainstem responses (ABR)].

Correlation function and power spectrum analyses were made for ABR of 20 normal ears and 14 ears with retrocochlear lesions. Power spectrum of normal ABR had three peaks, F0, F1 and F2; their frequencies being 125, 552.5, 967.5Hz respectively; the spectrographic shapes were of good similitude. The curve of cross correlation function in normal ABR was V-shaped, with the valley at 6-8 ms delay. In ABR of the retrocochlear lesions, the peaks of power spectrogram appeared lower and smoother with F1, F2 shifting to left and varying obviously. Their curves of cross correlation function were even and had no regular pattern. We have found that, F1 and F2 shift may be a characteristic of hearing disorder and the analysis of cross correlation function could help for the detection of useful signal from distorted signals.

Auditory Diseases, Central↗
PubMed1990

[Histopathological studies on glottic cancer by serial sections].

In 31 glottic cancer specimens from partial laryngectomy, the histopathological findings were compared with vocal cord motility and 5-year survival rate. Among the 31 cases, 7 had ventricular involvements, in which 3 were transglottic tumors; 2 had had their framework destroyed. Eight cases had anterior commissure involvement. Only one had the tendon affected. Of 20 cases with mobile cords, the lesions were entirely superficial to the conus elasticus. Only a few specimens showed minimal invasions of the arytenoid region. Of 8 cases with limited vocal cord motility, invasion of the thyroarytenoid muscle was quite apparent, 4 specimens had the arytenoid areas surrounded by nests of tumor cells, and one case had local recurrence 12 months after operation. There were 3 cases with vocal cord fixation, 2 with subglottic extensions showed cricoid cartilage involvement and had had recurrences 10 and 12 months after operation. Another one with transglottic lesion was controlled by middle portion subtotal laryngectomy. Nine cases had subglottic involvement. One with transglottic lesion had recurrence, the other with arytenoid invasion had local recurrence. In two more recurrent cases, tumors cells spreaded submucosally toward the infraglottic area.

Adult↗
PubMed1989

Dietary marine lipids suppress murine autoimmune disease.

Dietary marine lipids reduce both mortality and the severity of glomerulonephritis in inbred murine strains which develop spontaneous autoimmune disease. The protective effects of marine lipids appear to be accounted for by the major n-3 fatty acids in these preparations, 20:5 and 22:6. The n-3 fatty acids in dietary fish oil are extensively incorporated into several lipid classes in the spleen of autoimmune mice, including phosphatidylinositol, phosphatidylethanolamine, plasmalogens and saturated ether-linked phospholipids as well as diacylphosphoglycerides. The effects of dietary marine lipids on autoimmune disease in experimental models are highly specific. Careful controlled trials will be required to establish the role of dietary marine lipids in the therapy of human autoimmune disease.

Animals↗
PubMed1989

Helicase, DNA-binding, and immunological properties of replication-defective simian virus 40 mutant T antigens.

Simian virus 40 T antigen (TAg) exhibits nonspecific and origin-specific DNA binding (ori binding) and ATPase and helicase activities, all of which are related to its roles in viral DNA replication. We have characterized some of the properties of four replication-defective but transformation-competent mutant TAgs, C6-2, T22, C11, and C8A. C6-2 and T22 TAgs were each previously determined to lack ori-binding properties, while C11 TAg was reported to lack ATPase activity. The C8A TAg did not exhibit defects in either ori-binding or ATPase functions. We have analyzed additional aspects of these mutant TAgs pertaining to their helicase, DNA-binding, and immunological properties. With the exception of the C11 TAg, all the other TAgs exhibited helicase activity. The lack of helicase activity by C11 TAg was consistent with its previously shown inability to hydrolyze ATP or to replicate viral DNA. These results therefore show that ori-binding and helicase activities are separate functions of TAg. Wild-type and mutant TAgs bound with similar efficiency to either native or denatured calf thymus DNA-cellulose, indicating no marked differences in their nonspecific DNA-binding properties. We also tested the binding of wild-type and mutant TAgs to a monoclonal antibody, PAb 100, that was previously shown to recognize an extremely small class of TAg that may represent a unique conformational form of the protein. Interestingly, while less than 10% of the wild-type, C6-2, C11, and T22 mutant TAgs were recognized by PAb 100, more than 60% of the C8A mutant TAg was bound by this antibody. Therefore, although no defect in biochemical function was observed with the C8A TAg, its deficiency in viral DNA replication may be related to an unusual conformation, as detected by its dramatically increased recognition by PAb 100. These results show that the helicase activity of TAg is not required for its transformation function.

Antibodies, Monoclonal↗
PubMed1989

Basement membrane and human epidermal differentiation in vitro.

To test the role of basement membrane in differentiation of human epidermis reconstituted on human dermis, we prepared dermis with and without basement membrane and cultured epidermal cells on these two dermal substrata. The absence of basement membrane components was confirmed by immunofluorescence staining for laminin and type IV collagen and by electron microscopy. A high degree of differentiation of reconstituted epidermis did not require basement membrane as shown by the development of basal, spinous, and granular cell layers, and synthesis of 58 and 65-67 kDa keratins when epidermis was attached directly to dermis. On the other hand, we found that the basement membrane regulated the adhesive interaction between the epidermis and dermis. On dermis with basement membrane, attached epidermal cells formed hemidesmosomes and mechanically stable bonding. In the absence of basement membrane, the epidermal cells did not form hemidesmosomes, and bonding between the epidermis and dermis was unstable. Moreover, dermis from which the basement membrane was removed was reorganized by the epidermal cell layer.

Basement Membrane↗
PubMed1989

[Simultaneous recording of electrocochleogram and auditory brainstem responses].

A method which can record and plot the electrocochleogram (ECochG) and auditory brainstem response (ABR) simultaneously with the same tracing was studied. The results demonstrated that the ECochG waves obtained by our method and that recorded alone were very similar. The -SP/AP values and the latencies of ABR obtained by those two methods had no statistically significant difference. It could help the recognition of ABR waves, particularly wave I. This technique was more beneficial in determination of wave I-V interpeak latencies and in differential diagnosis between cochlear and retro-cochlear lesions.

Adolescent↗
PubMedDate not supplied

Lymphocyte phenotypes at tumor margins in patients with head and neck cancer.

Lymphocyte phenotypes were identified by monoclonal antibodies and avidin-biotin peroxidase reagents and enumerated in tumor tissue removed from 26 patients with head and neck cancer. T lymphocytes (T11) were the predominate phenotype at the tumor margin, with twice as many helper/inducer (T4) as suppressor/cytotoxic (T8) lymphocytes. Patients with Stage II and III carcinoma of the glottis, tongue, and hypopharynx had significantly increased numbers of all T lymphocyte phenotypes when compared to patients with Stage IV disease, thus achieving statistical significance for the T11 and T8 phenotypes. All patients were followed for 2.5 years; those patients who remained free of malignant disease had an increased number of all T lymphocyte phenotypes compared to patients with recurrent malignancy, but this did not achieve statistical significance. Thus, increased numbers of T11 positive lymphocytes of both the T4 and T8 subsets in the tissue at the margins of head and neck tumors were associated with a more favorable prognosis. These results support the concept of an immunologic reaction at the tumor margin, which may be limiting the growth and spread of tumor.

Carcinoma, Squamous Cell↗
PubMedDate not supplied

Novel neurite growth-inhibitory properties of an astrocyte proteoglycan.

Conditioned medium (CM) of primary cultures of GFAP-positive adherent astrocytes from neonatal rat neocortex contained a chondroitin sulphate/dermatan sulphate proteoglycan (CDSPG) that co-eluted with a heparan sulphate proteoglycan (HSPG) by ion-exchange chromatography. The CDSPG was resolved from the HSPG by molecular sieve chromatography, which indicated that the molecular mass of the HSPG was greater than 300 kDa, while that of the CDSPG was approximately 50 kDa. Specific lyase digestion and urea/polyacrylamide gel electrophoresis established the homogeneity of the CDSPG and suggested molecular masses of the core protein and glycosylated protein as 54 kDa and 58 kDa respectively. Virtually all of the poly-D-lysine substrate-bound proteoglycan-associated neurite growth-promoting activity of astrocyte CM was accounted for by the HSPG. On poly-D-lysine the immobilized CDSPG displayed little neurite growth-stimulatory activity relative to the HSPG. However, the CDSPG inhibited the potent growth-promoting activity of the HSPG by displacing it from the poly-D-lysine substrate. Differential cellular regulation of production of growth-modulatory proteins with different binding avidity for the substrate of growth may determine the success of a regenerative axonal response by fully competent neurons.

Animals↗
PubMedDate not supplied

RFLP analysis of preferential transmission in interspecific hybrids of Phaseolus vulgaris and P. coccineus.

The inheritance of RFLP markers in interspecific hybrids of Phaseolus vulgaris and P. coccineus was analyzed. Of 280 cDNA probes used, 70%-85% revealed polymorphism between species while intraspecific RFLP ranged from 8% to 37%. Segregation of 63 clearly scorable markers was examined in 177 P. vulgaris x P. coccineus F2's maintained as callus. Preferential transmission of the P. vulgaris alleles was observed for 24 of the 28 loci exhibiting non-Mendelian ratios. Although the segregation ratios at 17 loci fit gametic selection, also other factors such as nuclear-cytoplasmic or embryo-endosperm interactions may be involved. In the reciprocal F2, a relatively high frequency of maternal alleles was recovered for several loci, while the paternal allele was favored at others. The cDNA clone detecting the most extreme segregation, with no P. coccineus type detected among 165 P. vulgaris x P. coccineus F2 progeny, showed high homology to histone H2A genes. The markers were mapped to nine linkage groups. Aggregation of markers with preferential maternal transmission was observed, which could be due to selection of individual chromosomes, although false linkage detection cannot be excluded. The results obtained with RFLPs may explain the skewed distribution of phenotypic traits following interspecific hybridization.

Amino Acid Sequence↗
PubMedDate not supplied

Duodenal somatostatinoma of the ampulla of vater diagnosed by endoscopic fine needle aspiration biopsy: a case report.

BACKGROUND: Duodenal somatostatinoma is a rare neuroendocrine neoplasm. A better prognosis can be obtained if these tumors are resected at an early clinical stage. Endoscopic punch biopsy has been the method most commonly used for the preoperative diagnosis of neuroendocrine duodenal tumors. To the best of our knowledge, endoscopic fine needle aspiration biopsy (FNAB) of duodenal somatostatinoma has not been reported before. CASE: A 41-year-old, black female presented with upper gastrointestinal bleeding as well as elevated bilirubin, liver enzymes and glucose. Computed tomography, esophagogastroduodenoscopy and endoscopic retrograde cholangiopancreatography (ERCP) detected a mass at the region of the ampulla of Vater partially obstructing the pancreatic duct. The initial punch biopsy yielded only intestinal mucosa. Subsequent endoscopic FNAB suggested the diagnosis of a neuroendocrine neoplasm, as confirmed by additional punch biopsies. Immunohistochemical and electron microscopic studies disclosed somatostatin production by the tumor, which was resected through a modified Whipple procedure. The patient recovered fully. CONCLUSION: This case demonstrates the usefulness of endoscopic FNAB in diagnosing submucosal gastrointestinal neuroendocrine tumors.

Adult↗