PubMed Health⌕ Search

Biomedical subjects

J C Byrd

Publications and source records attributed to J C Byrd.

At least 127 records · Page 7Linked to original sources
PubMed1990

Effects of membrane fluidity on [3H]TCP binding to PCP receptors.

Phencyclidine (PCP) binds with high affinity to the ion channel associated with the NMDA receptor. The binding of the PCP receptor-specific ligand TCP is greatly reduced at temperatures between 2 degrees C and 6 degrees C, at which the plasma membrane is in a rigid state. However, membrane rigidity alone does not appear to cause the reduced TCP binding, since the membrane fluidizing agent A2C did not increase TCP binding at 4 degrees C; instead, it decreased binding at 21 degrees C. This inhibitory effect of A2C on TCP binding was dose dependent and was highly correlated with A2C-induced increases in membrane fluidity. The IC50 of A2C inhibition was 8.9 mM, with a pseudo-Hill coefficient of -0.24. Scatchard analysis demonstrated that this effect was the result of an increase in the apparent KD of [3H]TCP for the PCP receptor, with no effect on the Bmax. These results suggest that the function of the NMDA-PCP receptor complex is impaired by increases in membrane fluidity. These findings may be pharmacologically relevant in understanding the mechanism of action of such agents as general anesthetics and ethanol, which cause increases in plasma membrane fluidity.

Animals↗
PubMed1990

Blood group antigen synthesis and degradation in normal and cancerous colonic tissues.

ABH antigens are expressed by colonic epithelial cells throughout the colon during fetal life but only in proximal segments during adulthood. Malignant and premalignant colonic tumors frequently exhibit ABH reappearance (distal lesions) or ABH deletion (proximal lesions) and occasionally express incompatible A or B substances. Mechanisms governing these developmental and cancer-associated alterations are unknown. Therefore, experiments were performed to assess the activities of biosynthetic (glycosyltransferase) and degradative (glycosidase) enzymes in normal and cancerous tissues of the proximal and distal colon. In normal colonic mucosa, A, B, and H transferase activities were similar in proximal and distal segments. Analysis of enzyme substrate affinities and product characterization confirmed that the ABH transferases in colonic tissues were similar to the gene-specified transferases in human serum. Glycosidase enzyme activities were also comparable in proximal and distal normal colon. Cancers had lower A and B transferase but similar H transferase activities compared with paired normal mucosa. Thus, the absence of ABH antigen expression in normal distal colon is not caused by insufficient glycosyltransferase activity or excessive glycosidase activity.

ABO Blood-Group System↗
PubMed1990

Expression of native and deglycosylated colon cancer mucin antigens in normal and malignant epithelial tissues.

Immunohistochemical techniques were used to determine the distribution and cellular location of the mature and precursor forms of a colonic-type mucin in normal and malignant epithelial tissues. The antisera used in this study were prepared against native human colon cancer mucin (LS), partially deglycosylated mucin (HFA or GalNAc-apomucin), and fully deglycosylated mucin (HFB or apomucin). These antisera reacted with most mucin-producing cells of the normal gastrointestinal tract, salivary ductular cells, bronchial epithelial cells, some bronchial mucous glands, and squamous epithelial cells of the esophagus. Breast, endometrium, ovary, prostate, liver, and thyroid were nonreactive. In most normal organs, HFB reactivity was present in the supranuclear and perinuclear cytoplasm and LS and HFA were located primarily in goblet cell vacuoles, apical cytoplasm, and luminal secretions. These findings are consistent with the expected subcellular locations of apomucin and more "mature" mucins. LS, HFA, and HFB were frequently expressed in adenocarcinomas of the colon, stomach, pancreas, and lung. Lymphoma, sarcoma, and melanoma specimens were nonreactive. Alterations in the expression of these mucin antigens in malignant tissues included loss of subcellular compartmentalization, increased intensity of staining, and disappearance of staining. In addition, de novo expression of HFB was observed in one of five breast carcinomas and three of five ovarian mucinous cystadenocarcinomas. These data demonstrate that LS, HFA, and HFB are useful for studying the organ specificities and biosynthetic pathways of one type of mucin in normal and malignant tissues.

Adenocarcinoma↗
PubMed1989

Inhibition of mucin glycosylation by aryl-N-acetyl-alpha-galactosaminides in human colon cancer cells.

Specific inhibitors of the glycosylation of O-glycosidically linked glycoproteins have not previously been described. When tested for their effects on mucin glycosylation in a mucin-producing colon cancer cell line, LS174T, benzyl-, phenyl-, and p-nitrophenyl-N-acetyl-alpha-galactosaminide inhibited the formation of fully glycosylated mucin in a dose-dependent manner. Free aryl-oligosaccharides were found in the medium of treated cells labeled with [3H]glucosamine, [3H]galactose, [3H]fucose, [3H]mannosamine, or phenyl-alpha-[6-3H] N-acetylgalactosamine. UDP-Gal:GalNAc-beta 1,3-galactosyltransferase was inhibited by aryl-N-acetyl-alpha-galactosaminides but not by a number of other aryl-glycosides. Treatment with these inhibitors also causes reversible morphologic changes including formation of intercellular cysts. Aryl-N-acetyl-alpha-galactosaminides can be useful for the structural and functional studies of mucin macromolecules and other O-linked glycoproteins.

Acetylgalactosamine↗
PubMed1989

ABH blood group antigen expression, synthesis, and degradation in human colonic adenocarcinoma cell lines.

The synthesis of blood group ABH antigens is under genetic control, where the primary gene products are glycosyltransferases. Several studies have demonstrated cancer-associated alterations in ABH antigen expression in human colon cancer tissues. However, the mechanism(s) responsible for these alterations has not been elucidated. Therefore, experiments were conducted using nine established colon cancer cell lines (four type O, three type A, and two type B) to examine ABH antigen expression by immunocytochemistry and correlate this with activities of ABH biosynthetic (glycosyltransferase) and degradative (glycosidase) enzymes. The products of the glycosyltransferase enzymes were characterized by high performance liquid chromatography and paper chromatography, and substrate affinities (apparent Km values) of the cancer cell-derived glycosyltransferases were analyzed. The present data demonstrate: (a) all cell lines except H-498 (blood type A) expressed the appropriate ABH glycosyltransferase as well as all three glycosidases; (b) product characterization and substrate dependence experiments suggested that the cancer cell-derived ABH glycosyltransferase enzymes had properties that were similar to those of the ABH enzymes in human serum; (c) H-498 cells exhibited A antigen deletion with accumulation of H precursor substance, most likely due to insufficient A transferase activity; (d) SW1417 cells (blood type B) demonstrated B antigen deletion without precursor accumulation, despite adequate levels of B transferase and low alpha-galactosidase activity; and (e) weak incompatible A antigen expression occurred in LoVo (type B) and SW1116 (type O) cells, and weak incompatible B antigen expression occurred in H-498 (type A) and SW1116 cells. However, since these cells lacked incompatible A or B transferase activity, these incompatible antigens are probably not the true A or B antigens. Thus, the colon cancer cell lines used in this study exhibit all of the ABH alterations previously described in colon cancer tissues and appear to be useful experimental models for studying the molecular events involved in cancer-associated ABH expression.

ABO Blood-Group System↗
PubMed1989

Deglycosylation of mucin from LS174T colon cancer cells by hydrogen fluoride treatment.

Mucin from xenografts of LS174T human colon cancer cells was treated with anhydrous HF for 1 h at 0 degree C to give a product (HFA) with over 80% of the glucosamine and hexose removed, but retaining some galactosamine, and for 3 h at room temperature to give a product (HFB) devoid of carbohydrate. Rabbit antibodies against HFA bound to HFA much more than to HFB, and bound to native mucin to an intermediate extent. Antibodies to HFB bound to HFB more than to HFA, and did not bind to native mucin. Both HFA and native mucin bound a number of lectins, but HFB did not. By SDS/polyacrylamide-gel electrophoresis and size-exclusion h.p.l.c., native mucin and HFA are of apparent molecular mass greater than 400 kDa, whereas HFB is heterogeneous and of low molecular mass. On Western blots, antibody to HFA detected both high-molecular-mass mucin and a 90 kDa protein in homogenates of LS174T cells. Antibody to HFB detected a major 70 kDa band as well as higher-molecular-mass species. In tissue sections of normal colon and colon cancers, antibody to HFA showed both cytoplasmic and extracellular staining, whereas antibody to HFB generally stained only cytoplasmic antigens. These results indicate that anti-HFB antibody is specific for apo-mucin, whereas anti-HFA antibody is specific for GalNAc-apo-mucin.

Animals↗
PubMed1989

Community hospital transfers to a VA Medical Center.

We prospectively studied all transfers from community hospitals to the Zablocki Veterans Administration Medical Center in Milwaukee (Wis) between May 28, 1986, and January 1, 1987. Transfers totaled 4.7% (311/6609) of acute-care admissions during the study period but accounted for 19.1% (39/204) of in-hospital deaths. The mortality rate for transferred patients who required Veterans Administration hospitalization was 12.5% (39/311) compared with 2.6% (165/6298) for all other admissions. At the time of transfer 59 patients (19%) were judged unstable by a modification of the APACHE II classification system, yet only 19 patients were cared for en route by a physician or a nurse. In addition to higher mortality, the transferred patients had a longer median length of stay than nontransferred patients (11 days vs 7 days).

Adolescent↗
PubMed1989

Expression of (+)-3-PPP binding sites in the PC12 pheochromocytoma cell line.

Phencyclidine binds with high affinity to both PCP and sigma receptors. We investigated whether the clonal cell line PC12 expressed either of these receptors, and found that these cells contain a haloperidol-sensitive (+)-[3H]3-PPP binding site with a KD of 56 nM, but no PCP binding sites. The (+)3-PPP binding sites in PC12 cells displayed a reversed stereoselectivity for the benzomorphan opiates compared to CNS sigma receptors. Neither nerve growth factor nor sodium butyrate treatment affected the expression of either (+)-3-PPP or TCP binding sites in PC12 cells.

Adrenal Gland Neoplasms↗
PubMed1989

Molecular cloning of human intestinal mucin cDNAs. Sequence analysis and evidence for genetic polymorphism.

A human small intestine lambda gt11 cDNA library was screened using antisera prepared against the deglycosylated protein backbone of human colon cancer xenograft mucin. Three cDNAs were isolated from this screening, designated SMUC 40-42. These cDNAs were all found to contain tandem repeats of 69 nucleotides which encoded a threonine- and proline-rich protein consensus sequence of PTTTPITTTTTVTPTPTPTGTQT. RNA blots probed with one of these cDNAs, SMUC 41, exhibited large, polydisperse hybridization bands at approximately 7,600 bases. Band intensities were strongest when human small intestine, colon, and colon cancer poly(A)+ RNA was used. In vitro translation of poly(A)+ RNA from human small intestine, colon, and colon cancer cells produced a 162,000-dalton peptide that was immunoprecipitated with antibodies to deglycosylated mucin. SMUC 41 was also used to probe DNA blots, which indicated the presence of restriction fragment length polymorphisms in the intestinal mucin gene. These findings may be important in assessing the abnormal mucins found associated with several human diseases.

Amino Acid Sequence↗
PubMed1989

Comparison of metabolically labeled mucins of LS174T human colon cancer cells in tissue culture and xenograft.

Colon cancer cells in culture synthesize and secrete mucin glycoproteins, which carry a number of cancer-associated antigens. However, the structures and mechanisms of biosynthetic processing are not well understood. Mucins synthesized and secreted by LS174T human colon cancer cells were compared to those in LS174T xenografts in athymic mice. Mucins radiolabeled with glucosamine or sulfate were purified by gel filtration and cesium chloride density gradient centrifugation. The mucins were of high molecular weight and were resistant to chondroitinase ABC, hyaluronidase and HNO2 treatment. They were, however, susceptible to pronase digestion and mild alkaline treatment. Using radiochemical precursors, the cellular mucin was shown to contain fucose, galactose, N-acetylgalactosamine, N-acetylglucosamine, N-acetylneuraminic acid, and sulfate. Oligosaccharides released by beta-elimination had N-acetylgalactosaminitol as the reduced amino sugar and also unreduced galactosamine, indicating that there is N-acetyl-galactosamine O-glycosidically attached to protein core and also peripheral N-acetyl-galactosamine not directly linked to protein. DEAE-cellulose chromatography of mucins showed two major peaks with both intracellular and secreted mucins, but xenograft mucins also had more acidic components. Sulfate-labeled mucins were shifted to less acidic peaks by neuraminidase digestion, which indicates that the same mucin molecules are both sialylated and sulfated. We conclude that the intracellular mucins of cultured colon cancer cells, those secreted into the medium, and those in nude mouse xenografts are chemically similar, but differ in sialic acid and sulfate content. This experimental model system, LS174T cells maintained in culture and as nude mouse xenografts, may be useful for further biosynthetic and structural studies of colon cancer mucin.

Animals↗
PubMed1989

Improving patient comprehension of literature on smoking.

This study was designed to determine if simplification of smoking literature improved patient comprehension. Subjects (N = 129) were randomized in three groups: to receive no smoking booklet, receive one written at the 5th grade, or the 10th grade reading level. Subjects receiving the 5th grade booklet showed 13 percent better comprehension than those receiving the 10th grade booklet, and 18 percent better than the controls. Comprehension of written smoking materials can be improved by adjustment of the reading grade level.

Adult↗
PubMed1989

The influence of smoking on vitamin C status in adults.

To further define the relation between smoking and vitamin C status, the dietary and serum vitamin C levels of 11,592 respondents in the second National Health and Nutrition Examination Survey (NHANES II) were analyzed. Smokers of 20 cigarettes daily had the lowest vitamin C dietary intake (79 mg, 95% CI:73, 84) and serum levels (0.82 mg/dl, 95% CI: 0.77, 0.86; 46.6 mumol/L, 95% CI: 43.7, 48.8), while smokers of 1-19 cigarettes daily had decreased vitamin C intake (97 mg; 95% CI: 90, 104 mg) and serum levels (0.97 mg/dl, 95% CI: 0.92, 1.03; 55.1 mumol/L, 95% CI: 52.2, 58.5) compared to respondents who had never smoked (109 mg, 95% CI: 105, 113 and 1.15 mg/dl, 95% CI: 1.11, 1.18; 65.3 mumol/L, 95% CI: 63.0, 67.0, respectively). This inverse association between both intake and serum levels of vitamin C and smoking was independent of age, sex, body weight, race, and alcoholic beverage consumption. Following further adjustment for dietary vitamin C intake, the negative correlation between cigarette smoking and serum vitamin C levels persisted. The risk of severe hypovitaminosis C (serum levels less than or equal to 0.2 mg/dl; 11.4 mumol/L) was increased in smokers, particularly when not accompanied by vitamin supplementation (odds ratio 3.0, 95% CI: 2.5, 3.6). These data suggest that even though smoking adversely affects preferences for vitamin C rich foods, the inverse association between smoking and serum vitamin C levels occurs independently of dietary intake.

Adolescent↗
PubMed1989

Patient literacy and the readability of smoking education literature.

This study was designed to determine if primary care clinic patients read at a level congruent to the reading grade level of available smoking literature. Reading estimates of smoking education literature (N = 49) ranged from grade 3 to college level (median = 9.5). Reading skills of 258 smoking patients were estimated by reported years of schooling (median = 10), and by scores on the Wide-Range Achievement Test (median = 6). A serious disparity existed between the reading estimates of smoking education literature and the literacy skills of patients in our sample.

Educational Status↗
PubMed1989

Smoking cessation in practice.

Smokers expect health care professionals to help them stop smoking. Brief physician advice effectively increases cessation rates and should be given in a supportive and positive atmosphere emphasizing short-term benefits of cessation. Accurate information on withdrawal, weight gain, and nicotine gum should be offered, and systematic follow-up should be provided.

Chewing Gum↗
PubMed1988

Isolation and characterization of colon cancer mucin from xenografts of LS174T cells.

The structure of colonic mucin, which is thought to be important in several diseases, including ulcerative colitis and colon cancer, is poorly understood. Mucin was isolated from nude mouse xenografts of the LS174T colonic adenocarcinoma cell line by gel filtration and CsCl density gradient centrifugation. The isolated mucin had a high content of threonine, serine, and proline, with 28% of the total amino acids O-glycosylated. The carbohydrates present were fucose, sialic acid, galactose, N-acetyl-glucosamine, and N-acetyl-galactosamine in the ratio of 0.4:1.5:1.0:0.9:1.4. Rabbit antibodies were prepared that recognized primarily protein-dependent determinants. By DEAE-cellulose chromatography, the purified mucin was found to be heterogeneous, with three major components that had small differences in carbohydrate composition. LS174T was antigenically and chromatographically similar to mucins in colon cancer tissue specimens and in nonmalignant colonic mucosae.

Adenocarcinoma↗