Biomedical subjects

J V Carter

Publications and source records attributed to J V Carter.

13 recordsLinked to original sources

PubMed2006

Insulin-like growth factor binding protein 3 has opposing actions on malignant and nonmalignant breast epithelial cells that are each reversible and dependent upon cholesterol-stabilized integrin receptor complexes.

IGF-binding protein (IGFBP)-3 is generally considered to have actions that counterbalance those of IGFs and is therefore being developed as a cancer treatment. In breast tumors, however, high levels are associated with aggressive tumors and poor prognosis. Consistent with this we have demonstrated that although IGFBP-3 and a non-IGF-binding fragment (serine phosphorylation domain peptide) reduced attachment and enhanced apoptosis of Hs578T breast cancer cells cultured on collagen or laminin, it promoted their attachment and survival on fibronectin, which is abundant in the matrix of aggressive tumors. We have now examined the factors that determine whether IGFBP-3 has positive or negative actions on breast epithelial cells. IGFBP-3 also promoted survival of Hs578T cells in the presence of an antibody to the beta1-integrin subunit or when cholesterol-stabilized complexes were disrupted. These actions were blocked by IGF-I or a MAPK inhibitor. Serine phosphorylation domain peptide had similar actions on MCF-7 cells that were again reversed on fibronectin or with disruption of cholesterol-stabilized complexes and blocked by the beta1-integrin antibody. In contrast, IGFBP-3 promoted growth and survival for nonmalignant MCF-10A cells, but these effects were again reversed on fibronectin and blocked by the beta1 antibody or a MAPK inhibitor or by disruption of cholesterol-stabilized complexes. On Hs578T cells, IGFBP-3 bound to caveolin-1 and beta1-integrins, enhancing their aggregation, the recruitment of focal adhesion kinase, and the activation of MAPK. In summary, with three breast epithelial cell lines, IGFBP-3 had positive or negative effects on growth and survival dependent upon the status of cholesterol-stabilized integrin receptor complexes.

Apoptosis↗

PubMed2001

Temporal and spatial expression patterns of TUB9, a beta-tubulin gene of Arabidopsis thaliana.

Transgenic plants carrying chimeric genes composed of segments of the 5'-flanking region of the Arabidopsis 9-tubulin gene (TUB9) fused to the coding region of the beta-glucuronidase (GUS) gene of Escherichia coli were used to investigate the temporal and spatial patterns of TUB9 expression. Chimeric genes that contained at least 800 bp of TUB9 5'-flanking DNA were expressed primarily in floral tissues, with high levels of expression observed in pollen, elongating pollen tubes and ovules. The expression of the reporter genes in ovules ceased at the time of fertilization. In situ hybridization was used to verify that the reporter gene expression in pollen of transgenic plants is representative of the patterns of expression of the endogenous TUB9 gene. In situ hybridization also provided new insight into TUB9 transcript accumulation in ovules. The possible role of TUB9 and the functional implication of the largely non-overlapping expression patterns of tubulin genes are discussed.

Arabidopsis↗

PubMed1998

Two beta-tubulin genes, TUB1 and TUB8, of Arabidopsis exhibit largely nonoverlapping patterns of expression.

Chimeric reporter genes were used to investigate the patterns of expression of two beta-tubulin genes, TUB1 and TUB8, in Arabidopsis thaliana. The TUB1 chimeric gene was preferentially expressed in epidermal and cortical cells of primary roots, whereas the TUB8 chimeric gene was preferentially expressed in the endodermal and phloem cells of primary roots and in the vascular tissues of leaves, stems, and flowers of transgenic plants.

Arabidopsis↗

PubMed1994

[Bioassay of rainbow trout (Oncorhynchus mykiss) pigmentation using ancho chili (Capsicum annuum) extracts].

Farming of trout requires a finishing diet containing pigments such as astaxanthin and canthaxanthin so that they may achieve a pink tissue coloration similar to that of wild trout. The production of synthetic pigments is not enough so that the requirements of the aquaculture industry are not met, besides having a high cost. Thus, the objective of the present study was to evaluate the deposition of saponified and esterified chili (Capsicum annuum) extracts in the skin and muscle of rainbow trout (Oncorhynchus mykiis). The experiment consisted of three treatments with the inclusion in the finishing diet of saponified and esterified chili extracts and of astaxanthin, respectively. Each treatment was carried out with 150 organisms with an average weight of a 150 g and done in duplicate. The results showed that both the saponified and esterified chili extracts pigmented the skin and muscle of rainbow trout, although the pigmentation effect was less red than that produced by the astaxanthin control.

Animal Feed↗

PubMed1992

Lithium decreases cold-induced microtubule depolymerization in mesophyll cells of spinach.

Freezing, dehydration, and supercooling cause microtubules in mesophyll cells of spinach (Spinacia oleracea L. cv Bloomsdale) to depolymerize (ME Bartolo, JV Carter [1991] Plant Physiol 97: 175-181). The objective of this study was to gain insight into the question of whether microtubules depolymerize as a direct response to environmental stresses or as an indirect response to cellular changes that accompany the stresses. Leaf sections of spinach were treated with Li(+) before and during exposure to low temperature. Treatment with Li(+) decreased the amount of microtubule depolymerization in cells subjected to low temperature, relative to a nontreated control, raising the possibility that the microtubules in these cells may not be inherently cold labile. Rather, microtubule depolymerization may be in response to cold-induced changes in concentration of cytoplasmic components.

Journal Article↗

PubMed1991

Microtubules in mesophyll cells of nonacclimated and cold-acclimated spinach : visualization and responses to freezing, low temperature, and dehydration.

Responses of cortical microtubules in spinach (Spinacia oleracea L. cv Bloomsdale) mesophyll cells to freezing, thawing, supercooling, and dehydration were assessed. Microtubules were visualized using a modified procedure for indirect immunofluorescence microscopy. Leaf sections of nonacclimated and cold-acclimated spinach were slowly frozen to various temperatures, fixed while frozen, and microtubules immunolabelled. Both nonacclimated and cold-acclimated cells exhibited nearly complete microtubule depolymerization after ice formation. After 1 hour thawing at 23 degrees C, microtubules in both nonacclimated and cold-acclimated cells repolymerized. With time, however, microtubules in nonacclimated cells again depolymerized. Since microtubules in cells of leaf tissue frozen slowly are subjected to dehydration as well as subzero temperatures, these stresses were applied separately and their effects on microtubules noted. Supercooling induced microtubule depolymerization in both nonacclimated and cold-acclimated cells, but to a smaller extent than did freezing. Exposing leaf sections to solutions of sorbitol (a cell wall-penetrating osmoticum) or polyethylene glycol 10,000 (a nonpenetrating osmoticum) at room temperature caused microtubule depolymerization. The effects of low temperature and dehydration are roughly additive in producing the observed microtubule responses during freezing. Only small differences in microtubule stability were resolved between nonacclimated and cold-acclimated cells.

Journal Article↗

PubMed1991

Effect of microtubule stabilization on the freezing tolerance of mesophyll cells of spinach.

Freezing, dehydration, and supercooling cause microtubules in mesophyll cells of spinach (Spinacia oleracea L. cv Bloomsdale) to depolymerize (ME Bartolo, JV Carter, Plant Physiol [1991] 97: 175-181). The objective of this study was to determine whether the LT(50) (lethal temperature: the freezing temperature at which 50% of the tissue is killed) of spinach leaf tissue can be changed by diminishing the extent of microtubule depolymerization in response to freezing. Also examined was how tolerance to the components of extracellular freezing, low temperature and dehydration, is affected by microtubule stabilization. Leaf sections of nonacclimated and cold-acclimated spinach were treated with 20 micromolar taxol, a microtubule-stabilizing compound, prior to freezing, supercooling, or dehydration. Taxol stabilized microtubules against depolymerization in cells subjected to these stresses. When pretreated with taxol both nonacclimated and cold-acclimated cells exhibited increased injury during freezing and dehydration. In contrast, supercooling did not injure cells with taxol-stabilized microtubules. Electrolyte leakage, visual appearance of the cells, or a microtubule repolymerization assay were used to assess injury. As leaves were cold-acclimated beyond the normal period of 2 weeks taxol had less of an effect on cell survival during freezing. In leaves acclimated for up to 2 weeks, stabilizing microtubules with taxol resulted in death at a higher freezing temperature. At certain stages of cold acclimation, it appears that if microtubule depolymerization does not occur during a freeze-thaw cycle the plant cell will be killed at a higher temperature than if microtubule depolymerization proceeds normally. An alternative explanation of these results is that taxol may generate abnormal microtubules, and connections between microtubules and the plasma membrane, such that normal cellular responses to freeze-induced dehydration and subsequent rehydration are blocked, with resultant enhanced freezing injury.

Journal Article↗

PubMed1990

Relationship between Freezing Tolerance of Root-Tip Cells and Cold Stability of Microtubules in Rye (Secale cereale L. cv Puma).

The response of cortical microtubules to low temperature and freezing was assessed for root tips of cold-acclimated and non-acclimated winter rye (Secale cereale L. cv Puma) seedlings using indirect immunofluorescence microscopy with antitubulin antibodies. Roots cooled to 0 or -3 degrees C were fixed for immunofluorescence microscopy at these temperatures or after an additional hour at 4 degrees C. Typical arrays of cortical microtubules were present in root-tip cells of seedlings exposed to the cold-acclimation treatment of 4 degrees C for 2 days. Microtubules in these cold-acclimated cells were more easily depolymerized by a 0 degrees C treatment than microtubules in root-tip cells of nonacclimated, 22 degrees C-grown seedlings. Microtubules were still present in some cells of both nonacclimated and cold-acclimated roots at 0 and -3 degrees C; however, the number of microtubules in these cells was lower than in controls. Microtubules remaining during the -3 degrees C freeze were shorter than microtubules in unfrozen control cells. Repolymerization of microtubules after both the 0 and -3 degrees C treatments occurred within 1 h. Root tips of nonacclimated seedlings had an LT-50 of -9 degrees C. Cold acclimation lowered this value to -14 degrees C. Treatment of 22 degrees C-grown seedlings for 24 h with the microtubule-stabilizing drug taxol caused a decrease in the freezing tolerance of root tips, indicated by a LT-50 of -3 degrees C. Treatment with D-secotaxol, an analog of taxol that was less effective in stabilizing microtubules, did not alter the freezing tolerance. We interpret these data to indicate that a degree of depolymerization of microtubules is necessary for realization of maximum freezing tolerance in root-tip cells of rye.

Journal Article↗

PubMed1990

Tubulin Isotypes in Rye Roots Are Altered during Cold Acclimation.

The cold stability of cortical microtubules in root-tip cells of winter rye (Secale cereale L. cv Puma) is altered by growth temperature (GP Kerr, JV Carter [1990] Plant Physiol 93:77-82). One hypothesis for the basis of this alteration is that different tubulin isotypes are present at different growth temperatures, and that the cold stability of microtubules is affected by these isotypic differences. We have explored the first part of this hypothesis by comparing protein extracts from roots of seedlings grown for 2 days at 22 degrees C (nonacclimated) or for an additional 2 or 4 days at 4 degrees C (cold-acclimated). Immunoblots of two-dimensional polyacrylamide gels were probed with monoclonal antibodies to alpha- and beta-tubulin. At least six alpha- and seven beta-tubulins were present in the extracts from both the nonacclimated and cold-acclimated roots. Changes in electrophoretic mobility and isotype number of both alpha- and beta-tubulin were observed after only 2 days at 4 degrees C. Further changes in tubulin were observed after 4 days at 4 degrees C. Changes in alpha-tubulin were more pronounced than those in beta-tubulin.

Journal Article↗

PubMed1983

Frost injury and heterogeneous ice nucleation in leaves of tuber-bearing solanum species : ice nucleation activity of external source of nucleants.

The heterogeneous ice nucleation characteristics and frost injury in supercooled leaves upon ice formation were studied in nonhardened and cold-hardened species and crosses of tuber-bearing Solanum. The ice nucleation activity of the leaves was low at temperatures just below 0 degrees C and further decreased as a result of cold acclimation. In the absence of supercooling, the nonhardened and cold-hardened leaves tolerated extracellular freezing between -3.5 degrees and -8.5 degrees C. However, if ice initiation in the supercooled leaves occurred at any temperature below -2.6 degrees C, the leaves were lethally injured.To prevent supercooling in these leaves, various nucleants were tested for their ice nucleating ability. One% aqueous suspensions of fluorophlogopite and acetoacetanilide were found to be effective in ice nucleation of the Solanum leaves above -1 degrees C. They had threshold temperatures of -0.7 degrees and -0.8 degrees C, respectively, for freezing in distilled H(2)O. Although freezing could be initiated in the Solanum leaves above -1 degrees C with both the nucleants, 1% aqueous fluorophlogopite suspension showed overall higher ice nucleation activity than acetoacetanilide and was nontoxic to the leaves. The cold-hardened leaves survived between -2.5 degrees and -6.5 degrees using 1% aqueous fluorophlogopite suspension as a nucleant. The killing temperatures in the cold-hardened leaves were similar to those determined using ice as a nucleant. However, in the nonhardened leaves, use of fluorophlogopite as a nucleant resulted in lethal injury at higher temperatures than those estimated using ice as a nucleant.

Journal Article↗

PubMed1981

Comparison of the structure and function of ribulosebisphosphate carboxylase--oxygenase from a cold-hardy and nonhardy potato species.

A comparison of ribulosebisphosphate carboxylase-oxygenase from the leaves of the nonacclimated, cold-hardy species, Solanum commersonii, and the nonacclimated, nonhardy species, Solanum tuberosum showed that this enzyme from the two species differed in structure and function. The results of sulfhydryl group titration with 5,5'-dithiobis(2-nitrobenzoic acid) indicated that the kinetics of titration and the number of accessible sulfhydryl groups in the native enzymes were different. After 30 min, the enzyme from the hardy species had 1.7 times fewer sulfhydryl groups titrated than that from the nonhardy species. In the presence of 1% (w/v) sodium dodecyl sulfate, the total number of sulfhydryl groups titratable with 5,5'-dithiobis-(2-nitrobenzoic acid) was the same for both species. However, this denaturant had a differential effect on the kinetics of titration with 5,5'-dithiobis(2-nitrobenzoic acid). Both enzymes had a native molecular weight of about 550 000. The quaternary structures of the two enzymes were similar with the presence of large and small subunits of 54 000 and 14 000, respectively. However, there was more polypeptide of 108 000--110 000 present in preparations of the enzyme from S. tuberosum than from S. commersonii. This polypeptide is an apparent dimer of the large subunit on a relative mass basis. The large subunit of the enzyme from S. tuberosum was more sensitive to the absence of reducing agent and was more sensitive to freezing and thawing than the large subunit of the enzyme from S. commersonii. Catalytic properties of both enzymes at 5 and 25 degrees C indicated no significant difference in the Km, CO2 at either temperature. However, the Vmax at 5 degrees C for the enzyme from S. commersonii was 35% higher than that of the enzyme from S. tuberosum. In contrast, the Vmax at 25 degrees C for the enzyme of the hardy species was 250% lower than that of the enzyme from the nonhardy species.

Acclimatization↗

PubMed1980

Lethal freeze-dehydration injury of dogwood stem tissue does not change the activation energy of water permeability.

The Arrhenius activation energy for water permeability, (DeltaE(a,H(2)O)) through stem cortical tissue of red osier dogwood (Cornus sericea L.) was determined after treatments which cause membrane rupture as well as after a lethal slow freeze and subsequent slow rewarming. The latter value was higher than the former, but was indistinguishable from the DeltaE(a,H(2)O) found for healthy tissue. It was concluded that membrane permeability to water is not altered during the first 24 to 48 hours after exposure of nonacclimated red osier dogwood to lethal freeze dehydration injury.

Journal Article↗

PubMed1978

Pressure effects on folded proteins in solution. Hydrogen exchange at elevated pressures.

The observed rate constants for base-catalyzed hydrogen exchange reactions between solvent water and peptide nitrogen in lysozyme, ribonculease A, oxidized ribonuclease A, and poly(DL-lysine) are all enhanced by an increase in pressure. Activation volumes have been calculated from the pressure effect on these rate constants. For the folded proteins lysozyme and ribonuclease A, deltaV for base-catalyzed exchange changes from about +9 ml/mol at atmospheric pressure -3 ml/mol at 2500 kg/cm2. The same quantity, determined for the random coil polypeptides oxidized ribonuclease A and poly(DL-lysine), does not show this dependence upon pressure. These effects can be understood either in terms of solvent penetration on the folded proteins or the onset of a small degree of pressure induced unfolding. Possible mechanisms by which such penetration could occur are discussed.

Hydrogen Bonding↗