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Biomedical subjects

L Warren

Publications and source records attributed to L Warren.

At least 73 records · Page 4Linked to original sources
PubMed1980

The membrane glycoproteins of the malignant cell.

Experiments are described and reviewed demonstrating that the bound carbohydrates of glycoproteins of many forms of malignant cells differ from their normal counterpart. The difference involves many oligosaccharide groups and is essentially quantitative. The characteristics of the difference are discussed. Despite the consistency of the finding its significance is unknown because the function of bound carbohydrates is largely unknown. Some properties of protein-bound carbohydrates that may be of special relevance to malignancy and other pathological processes are considered. The array of structures found in the cell is highly complex but seems to be similar in man, hamster, mouse, chick and fish. On the other hand, the biosynthesis of these structures can be influenced and altered by the environment and by drugs; the cell is tolerant of variation in its bound carbohydrate; microheterogeneity of the carbohydrates is probably the rule rather than the exception; experiments to test the function of bound carbohydrate show only small effects. A role for the bound carbohydrates in evolution is proposed that is consistent with these characteristics. It is also postulated that altered, bound carbohydrates of most glycoprotein does not endanger the life of the cell but may be responsible for involvement and change of many processes some of which permit the malignant cell to divide persistently and to prosper.

Animals↗
PubMed1979

The detection of smooth muscle desmin-like protein in BHK21/C13 fibroblasts.

Three distinct proteins, actin (42,000 daltons), the principal form of fibroblast 10 nm filament protein (55,000 daltons), and a protein with a molecular weight of 52,000 and a pI of 5.8 were detected in nonionic detergent-insoluble cytoskeletal and 10 nm filament preparations of control BHK21/C13 and line 9 hamster fibroblasts. Cytoskeletal preparations of other hamster fibroblast cell types, such as NIL8 and primary embryo fibroblasts, contained the 55,000-dalton component but lacked the 52,000-dalton protein. A Rous sarcoma virus transformant of the BHK21/C13 line and an adenovirus transformant of line 9, resembled the NIL8 and other fibroblast types in that they contained only the 55,000- and 42,000-dalton polypeptides. The identity of the 52,000-dalton protein in BHK21/C13 cells was studied. This protein co-electrophoreses on both one- and two-dimensional polyacrylamide gels with the predominant muscle form of 10 nm filament protein. Further, one-dimensional peptide maps of the hamster smooth muscle 10 nm filament protein and the hamster fibroblast 52,000-dalton protein are identical to one another and distinct from the peptide maps of both the 42,000- and the 55,000-dalton components of the fibroblast cytoskeletal preparations. We conclude that BHK21/C13 cells contain both the fibroblast and the muscle form of 10 nm filament protein.

Animals↗
PubMed1979

Isolation and characterization of the erythrocyte surface membrane of the smooth dogfish, Mustelus canis.

1. The plasma membrane of the dogfish erythrocyte is characterized. 2. Surface membranes were isolated from dogfish red cells. 3. Cells suspended in a hypotonic zinc chloride buffer (0.5 mM ZnCl2, 5 mM Tris-HCl, pH 8.0) tended to enucleate spontaneously. 4. By gentle homogenization relatively high yields of red cell "ghosts" were formed; these were purified using discontinuous gradients of sucrose and of glycerol solutions. Analyses of protein, carbohydrates and lipids were carried out. 5. There did not appear to be marked overall differences in the composition of the surface membrane of the nucleated dogfish erythrocyte compared to those of other species.

Amino Acids↗
PubMed1979

Alterations of membrane glycoproteins in malignant cells.

Comparisons have been made of the carbohydrates bound to membrane proteins of control and malignant cells in culture. It has been found that most individual glycoproteins of control and malignant cells differ in their carbohydrate components. Differences between control and malignant cells have been foundin the glycoproteins of the various membrane systems (surface, nucleus, mitochondria, endoplasmic reticulum). It is suggested that the extensive changes in bound carbohydrates of the malignant cell permit the cell to live and divide but isolate the cell functionally. The extensive structural changes may also be responsible for the cascading of involvement of various processes within the malignant cell.

Animals↗
PubMed1978

Glycopeptides derived from individual membrane glycoproteins from control and Rous sarcoma virus-transformed hamster fibroblasts.

The membrane glycoproteins from control (BHK21/C13) and Rous sarcoma virus-transformed (C13/B4) baby hamster kidney cells grown in medium containing [14C]- or D-[3H]glucosamine have been separated into two distinct classes: a phenol-soluble fraction and an aqueous fraction. The membrane glycoproteins from both BHK21/C13 and C13/B4 partitioned similarly into these two fractions. The phenol and aquesous-soluble glycoproteins differed in their sodium dodecyl sulfate-polyacrylamide gel profiles, polyacrylamide isoelectric focusing profiles, and glycopeptide distribution on Sephadex G-50. A number of aqueous and phenol-soluble glycoproteins from BHK21/C13 and C13/B4 cells were purified to near homogeneity by means of polyacrylamide electrophoresis and gel electrofocusing. These glycoproteins range in molecular weight from 179,000 to 31,000 and have isoelectric points of 7.5 to 3.0. Our results show that the pronase glycopeptides of 20 out of 24 homologous membrane glycoproteins of equivalent molecular weight and isoelectric point from BHK21/C13 and C13/B4 cells are dissimilar as measured by Sephadex G-50 gel filtration.

Avian Sarcoma Viruses↗
PubMed1977

Purification of alpha-L-fucosidase from various sources by affinity chromatography.

An affinity column for alpha-L-fucosidases was constructed by linking p-amino-phenyl 1-thio-alpha-L-fucopyranoside to Sepharose 4B through linkers of succinyl 3,3'-diamino-dipropylamine. Excellent purification of alpha-L-fucosidase from rat epididymis, Clostridium perfringens and Limulus polyphemus (horse shoecrab) could be effected inone step with good yield. An affinity column purification step can be introduced at any point in published purification procedures. The purified enzyme is essentially free of other glycosidases and proteolytic enzymes. The column material is stable and can be reused for at least two years.

Animals↗
PubMed1977

Purification of beta-N-acetyl-D-glucosaminidase of the horseshoe crab by affinity chromatography.

An affinity column has been synthesized consisting of p-aminophenyl 1-thio-beta-L-fucopyranoside residues attached to Sepharose 4B through succinylated diaminodipropylamine bridges. Surprisingly, it has been found to bind beta-N-acetylglucosaminidase in the serum of Limulus polyphemus (horseshoe crab). The enzyme is eluted with N-acetyl-D-glucosamine at a concentration of 2 mg/ml and with other sugars at higher concentrations. A highly purified enzyme free from other glycosidases is obtained. The enzyme is not eluted by solutions of salt.

Acetylglucosaminidase↗
PubMed1977

Colloidal iron hydroxide-binding to the surfaces of chick embryo fibroblasts transformed by wild-type and a temperature-sensitive mutant of Rous sarcoma virus.

The densities of colloidal iron hydroxide (CIH) particles binding to the surfaces of chick embryo fibroblasts were determined before and after transformation with wild type Rous sarcoma virus and a temperature sensitive (ts) mutant of this virus. On the basis of in vitro behavior, cells transformed by the ts virus manifest a malignant phenotype at 36 degrees C (permissive temperature) and appear normal at 41 degrees C (non-permissive temperature). At the permissive temperatures there is a significant increase in CIH particle-binding to spaces of cell surface between microvilli on the wild type and ts transformed cells. At the non-permissive temperature this significant increase in binding is only observed on the wild type transformant, while the density found on the ts transformant is not significantly different from the untransformed state. Therefore, in vitro characteristics of normalcy and malignancy are reflected in changes in the CIH binding properties of the cell surface spaces between microvilli. The CIH densities observed on the microvilli are significantly different from the density on the spaces between them for each of the classes of cells studied at either temperature. The microvilli are found to bind a lower density of particles in five of the six cases. No correlations between microvilli particle density and transformation to in vitro malignant characteristics were observed.

Animals↗
PubMed1977

Is there a role for actin in virus budding?

Electrophoretic data from both sodium dodecyl sulfate-polyacrylamide gels (SDS-PAGE) and acid-urea gels reveal a protein in purified murine mammary tumor virus (MuMTV) which co-migrates with purified chick skeletal muscle actin. 125I-labeling of intact and disrupted virus preparations shows that the actin-like protein is not artifactually adsorbed to the outside of virions during isolation. Quantitative SDS-PAGE and examination of negatively stained preparations show that the actin cannot be accounted for by a contaminating population of virus-free vesicles. The ultrastructure of mammary epithelial cells and of Rous sarcoma virus-transformed chick embryo fibroblasts shows that virus extrusion is associated with filament-containing cellular processes. In particular, MuMTV is released from the ends of long microvilli which contain a bundle of 6-8-nm microfilaments and share other structural features with intestinal microvilli. We suggest that virus nucleoids require an interaction with host cell contractile proteins for their extrusion from the cell.

Actins↗
PubMed1976

The repair of the surface structure of animal cells.

Experiments were performed to determine if animal cells in culture possess specific mechanisms to repair surface molecules damaged by enzymes. The surface membranes of a primary cell culture, chick fibroblasts, a permanent hamster cell line, BHK21/C13, and its virally transformed counterpart, C13/B4 were damaged by exposure to trypsin or to neuraminidase. Following digestion with trypsin, the incorporation of radioactive amino acids or sugars into purified surface membrane of cells was monitored. No differences were noted in rates of incorporation when control and trypsin-damaged cells were compared. Neuraminidase damage to the surface of BHK21/C13 and C13/B4 cells was evidenced by altered gel filtration profiles of surface glycopeptides, i.e., delayed elution because of reduction in size. By labelling cells with 14C-L-fucose prior to neuraminidase treatment and following the incorporation of 3H-L-fucose into cell surface glycopeptides after neuraminidase digestion, we were able to monitor the synthesis and turnover of fucose-containing glycopeptides in the same cells. Gel filtration profiles indicated that little or no desialylated glycoproteins were resialylated (repaired) by specific replacement of sialic acid. Comparing neuraminidase-digested and control cells we observed no difference in rates of 3H-L-fucose incorporation or of 14C-L-fucose loss from these cells; nor did we find differences in the rate of incorporation of isotopic glucosamine into sialic acid. Neuraminidase treatment failed to alter the rate of cell growth or the pattern of isotopic incorporation into various cell surface components. These results support the suggestion that return of sialic acid (repair) was effected by turnover which serves as a non-specific repair mechanism to replace damaged cell surface molecules (Warren and Glick '68; Warren, '69).

Cell Line↗
PubMed1975

The surface glycoproteins of a mouse melanoma growing in culture and as a solid tumor in vivo.

B16 melanotic tumors in various organs of mice were labeled with either [14C- or [3H]L-fucose or D-glucosamine. Glycopeptides derived from the membrane glycoproteins of these tumors were compared with those of normal tissues by double-label elution patterns from Sephadex G-50 columns. A marked increase of sialic acid-rich, fucose-containing glycopeptides (PEAK A) was found in the glycoproteins of the surface and internal membranes of melanotic cells. The glycopeptides from the melanoma cells could be reduced in size by treatment with neuraminidase. Comparison of the glycopeptide patterns of melanoma cells grown in culture and in mice revealed a greater complexity in in vivo material. Virtually all of the glycopeptides from melanoma cells grown in culture were of the larger type (Peak A) that correlates well with the malignant state. Comparison of two lines of B16 melanoma cells with greatly differing abilities to form tumors in lung revealed no significant, reproducible differences in their glycopeptide patterns.

Animals↗