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J F Harris

Publications and source records attributed to J F Harris.

48 records · Page 3Linked to original sources
PubMed1978

Regulation of immunoglobulin biosynthesis in the murine plasmacytoma MOPC 315.

We have examined certain aspects of IgG biosynthesis by constructing hybrids between MPC11 (gamma2b, kappa) and MOPC 315 (alpha,lambda2) that have lost the ability to synthesize one or the other heavy chain. Cells express the three chains in a stable fashion, and both autologous (parental) and heterologous (nonparental) H and L chain pairs form and are secreted. The alpha H chain was found in polymeric form when associated with the heterologous kappa L chain. The lambda2 L chain covalently assembled to the heterologous gamma2b H chain. Surprisingly, autologous pairing was always favored over heterologous pairing in vivo by 5 to 10:1 in terms of rate of assembly. Similar ratios were maintained in the secreted protein. These results suggest that co-expression of particular H and L chain pairs is predetermined. Evolution presumably operates to improve antigen recognition as well as rate of assembly of active molecules.

Animals↗
PubMed1977

Segregation studies in CHO hybrid cells: I. Spontaneous and mutagen-induced segregation events of two recessive drug-resistant loci.

The process of segreation or phenotypic expression of two recessive drug-resistant loci from heterozygous Chinese hamster ovary hybrid lines is examined. The spontaneous segregation rates of phytohaemagglutinin resistance (Phar) and a temperature-dependent 8-azaguanine-resistant locus (Azarts) from heterozygous quasitetraploid lines using Luria-Delbruck fluctuation analysis were 5 X 10(-5) and 10(-5) events/cell/generation, respectively. In quasihexaploid lines, the latter rates increased 40- and 200-fold, respectively, and were dependent on the number of presumptive drug-sensitive allelel. The mutagens EMS, MNNG, ICR-170, ICR-191, and gamma rays significantly increased the frequency of segregation events. The mutagen-induced frequency of dominant mutations to ouabain (Ouar) and alpha-amanitin (Amar) rsistance in the same hybrid line was much lower in comparison to segregation events and was mutagen specific. The chromosome number per metaphase cell was more variable than DNA content in quasitetraploid lines. These properties of marker segregation are consistent with mechanisms of either restricted chromosome loss, rearrangement, or mutation.

Azaguanine↗
PubMed1976

Primer dependency of glycogen synthetase during differentiation in Dictyostelium discoideum.

The cellular slime mold, Dictyostelium discoideum, has a life cycle in which the limited number of cell types and easily recognizable stages of development offer a unique model to relate biochemical events to differentiation. Ultramicrochemical techniques were employed to assay enzyme activity and product levels in cell samples as small as 0.02 mug of dry weight in reaction volumes of 0.1 mug. The techniques utilized an amplification procedure employing the enzymatic cycling of pyridine nucleotides. Glycogen synthetase (glucose 6-phophate independent form) was assayed in individual organisms over the time course of development. From aggregation to culmination, activity decreased and was dependent on soluble glycogen primer. From culmination to sorocarp stage, enzyme activity was independent of soluble glycogen primer. Further, the enzyme and its glycogen product were recovered in a low-spin (2000g) pellet fraction from sorocarp homogenates. The change in primer requirements and solubility of enzyme and product occurred during culmination. Localization studies in developing spore cells revealed trends in enzyme activities and solubilities of enzyme and product similar to those in whole organisms. Possible models of cell-specific biochemical events in D. discoideum are discussed.

Cell Differentiation↗
PubMed1976

Localization of glycogen synthetase during differentiation of presumptive cell types in Dictyostelium discoideum.

Ultramicrochemical techniques were utilized to assay glycogen synthetase (EC 2.4.1.11) activity in cell samples of Dictyostelium discoideum as small as 0.01 mug (dry weight) in reaction volumes of 0.1 mul. The activity was assayed by an amplification procedure employing the enzymatic cycling of pyridine nucleotides. These techniques were used to determine the extent of localization of glycogen synthetase in the two cell types during differentiation of D. discoideum. Localization studies in developing spore cells revealed decreasing enzyme activity to the culmination stage. During this phase of development, the enzyme required the presence of soluble glycogen for activity. From culmination to sorocarp stage, enzyme activity increased and was independent of the soluble glycogen. In developing stalk cells, synthetase showed a decreasing gradient of activity. In sorocarps, the cells in the stalk apex showed synthetase activity similar to that of the spores. The cells at the bottom of the stalk had no detectable activity.

Cell-Free System↗
PubMed1974

The analysis of spiral growth in phycomyces using a novel optical method.

A conical mirror was designed and used to measure simultaneously the elongational and rotational displacement of a number of markers on the growing zone of the sporangiophore of Phycomyces. The results obtained by this new optical method demonstrate that the rotational rate is roughly proportional to the elongational rate, except in the lower region of the growing zone where a significant amount of rotation occurs without measurable elongation. From the data presented in this report, we have constructed a model that appears to explain the mechanism responsible for the left-handed spiral growth of the developing sporangiophore.

Journal Article↗
PubMed1971

Snake infrared receptors: thermal or photochemical mechanism?

It appears that the two most sensitive infrared receptors known in the biological world are found in two widely different families of snakes, the pit vipers and the boas. After an infrared stimulus from a carbon dioxide laser, which has a monochromatic output at 10.6 micrometers, we find evoked potentials in boas with chronically implanted electrodes. Our data suggest that the receptors operate on a thermal principle.

Animals↗
PubMedDate not supplied

Modulation of clonal progression in B16F1 melanoma cells.

We have examined the effects of the microenvironment on the frequency and generation of metastatic variant cells in both parental B16F1 melanoma cells and nascent clones. The metastatic abilities of cultured B16F1 cells were tested after a period of growth in the presence or absence of a second cell population separated from each other by a transwell membrane (0.45 micron pore size). The first population is defined as the 'responder' cells and the second as the 'stimulator' cells. We found that the presence of 10(5) B16F1 stimulator cells during the growth of responder B16F1 cells from approximately 10(4) to approximately 10(6) cells resulted in cells with an increased metastatic phenotype (greater than 8-fold increase in median number of lung tumors relative to untreated B16F1 parental cells). The presence of stimulator cells also increased the metastatic phenotype of nascent clones, which were grown to a population size of less than 10(6) cells, suggesting that the rate of generation of metastatic variants of the responder B16F1 clones was affected by the stimulator cells. Other cell lines, including highly metastatic B16F10 and BL6 melanoma cells, and KHT35-L1 fibrosarcoma cells, were effective stimulator cells when as few as 10(4) cells were added to transwells. In addition, normal immortalized NIH 3T3 cells were effective stimulator cells only at 10(5) cells/transwell. The cell density at which untreated parental B16F1 cells were harvested (3 x 10(3)-3 x 10(5) cells/cm2) did not affect the median number of lung tumors significantly. These results suggest that factors released from both tumor and immortalized normal cells can modulate epigenetic changes in the metastatic phenotype of B16F1 melanoma cells.

Animals↗
PubMedDate not supplied

Dynamic heterogeneity: metastatic variants to liver are generated spontaneously in mouse embryonal carcinoma cells.

Mouse embryonal carcinoma (EC) cells derived from F9 cells form predominantly liver tumors following the intravenous injection (i.e. experimental metastasis assay) of EC cells into syngeneic 129/J male mice. In this study, EC cells (OTF9) expressing stage-specific embryonic antigen-1 (SSEA-1) are compared with cells (SOTF9) lacking SSEA-1 antigen in the experimental liver metastasis assay. When parallel clones of EC cells were grown to a measured cell number and tested in the experimental metastasis assay, it was observed that the frequency of experimental liver metastases increases with the population size. When the clonal population size is less than the critical number of cells (approximately 2 x 10(5) cells), the frequency of liver tumors is reduced relative to that of the parent EC population. The metastatic ability of clones derived from individual liver metastases did not differ from that of the parental cells. An analysis of the recessive biochemical and immunochemical markers of parental cells and of independent liver metastases suggests that somatic hybridization to host cells by the EC cells is not involved. These results are consistent with predictions from our dynamic heterogeneity model that was formulated by examining the experimental lung metastasis of KHT fibrosarcoma and B16 melanoma cells. Mathematical analysis of the results indicates that the effective rate of generation of the liver metastasizing variant cells is (7 +/- 3) x 10(-6) per cell per generation for both OTF9 and SOTF9 cells.

Animals↗
PubMedDate not supplied

Sulfated glycoconjugate determinants recognized by monoclonal antibody, SG-1, correlate with the experimental metastatic ability of KHT fibrosarcoma cells.

We have examined the binding and functional activity of monoclonal antibody (MAb) SG-1 that was raised by immunization against embryonal carcinoma cells and screened using KHT fibrosarcoma cells. Quantitative absorption, binding and in situ immunochemical staining assays indicate that the MAb SG-1-defined epitopes are expressed preferentially by the highly metastatic KHT35-L1 cells relative to the weakly metastatic, parental KHTp cells. Furthermore, there was a significant correlation (p less than 0.05) between the expression of MAb SG-1-defined antigen on the cells, following trypsin treatment, and their metastatic ability. Binding of MAb SG-1 to antigen was inhibited by specific sulfated polysaccharides including cerebroside sulfate (brain sulfatide), fucoidan, and dextran sulfate (500 kD) but not by heparan, chondroitin, keratan or dextran (5 kD) sulfates. Initial characterization of antigen from KHT cells indicates that the epitope of MAb SG-1 is defined by sulfated glycoconjugates containing galactose and sulfate but not N-acetylglucosamine. In the total lipid extracts of KHT35-L1 cells the antigen was detected in the delipidated protein fraction as well as in the chloroform/methanol fraction. These results suggest that the sulfated glycoconjugate determinants identified by MAb SG-1 may be relevant to the metastatic process of KHT fibrosarcoma cells.

Animals↗