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C L Campbell

Publications and source records attributed to C L Campbell.

18 recordsLinked to original sources
PubMed1994

Mitochondrial morphological and functional defects in yeast caused by yme1 are suppressed by mutation of a 26S protease subunit homologue.

The absence of functional Yme1p, a putative ATP and zinc-dependent protease localized to mitochondria of yeast, results in abnormal mitochondrial function and morphology. Yeast lacking Yme1p lose DNA from mitochondria at an accelerated rate, fail to grow on nonfermentable carbon sources at 37 degrees C, and have severely deficient growth if mitochondrial DNA suffers large deletions or is completely lost. In place of the normal reticulated mitochondrial network, strains lacking Yme1p have punctate mitochondria with some grossly swollen compartments. The growth phenotypes and morphological alterations evident in these mutant yeast can be compensated by a mutation in YNT1, an essential gene in yeast. The sequence of the YNT1 gene product indicates that it is one of a number of related regulatory subunits of the 26S protease. This proteolytic activity is necessary for progression through the cell cycle and has been implicated in the regulation of transcription. Ynt1p is more distantly related to Yme1p.

ATP-Dependent Proteases↗
PubMed1991

Rat enterocyte injury by oxygen-dependent processes.

Neutrophils migrate to areas of inflammation and, when stimulated, produce O2-, H2O2, and other reactive O2 metabolites. To assess the effects of stimulated neutrophils on enterocytes, rat enterocytes were incubated with peripheral neutrophils. To assess cell viability, trypan blue exclusion and lactate dehydrogenase and protein release were measured. When 10(6) enterocytes/mL were incubated with 2.5 x 10(5) neutrophils/mL stimulated with phorbol myristate acetate, trypan blue exclusion decreased and lactate dehydrogenase and protein release increased. With the addition of 0.10 mg/mL of superoxide dismutase, trypan blue exclusion further decreased and lactate dehydrogenase and protein release increased. This suggests that H2O2- or H2O2/O2(-)-derived metabolites are more damaging to isolated enterocytes than O2-. To test this hypothesis, enterocytes were incubated with xanthine and increasing concentrations of xanthine oxidase in the presence and absence of superoxide dismutase. With increasing concentrations of xanthine oxidase, the cell number decreased and protein release increased. With the addition of superoxide dismutase, fewer cells were present, suggesting that cell lysis occurred. Protein release was further increased by the addition of superoxide dismutase. Enterocytes were then incubated with leucine and increasing concentrations of amino acid oxidase. With increasing concentrations of amino acid oxidase, trypan blue exclusion decreased and protein and lactate dehydrogenase release increased. These effects were ameliorated by the addition of 500 IU catalase/mL. These data suggest that O2- and H2O2, whether created by stimulated neutrophils or an enzyme-generating system, are damaging to isolated enterocytes. Superoxide dismutase did not offer enterocytes protection.

Animals↗
PubMed1985

Production of zearalenone, T-2 toxin, and deoxynivalenol by Fusarium spp. isolated from plant materials grown in North Carolina.

Fusarium spp. isolated from plant materials grown in the hot, humid climate of North Carolina were tested for production of mycotoxins. Isolates of F. acuminatum, F. graminearum, F. moniliforme, F. oxysporum, and F. solani produced zearalenone while isolates of F. equiseti and F. graminearum produced T-2 toxin and deoxynivalenol, respectively. This is the first report of zearalenone production by F. solani. The toxins were identified by capillary gas chromatography-mass spectrometry. These findings suggest that there are toxigenic strains of Fusarium indigenous to the warmer regions of the USA and that fasariotoxicoses of animals in this region are not necessarily the result of importing toxic grains from the cooler, upper midwestern USA.

Animal Feed↗
PubMed1983

Folate utilization in Friend erythroleukemia cells.

In order to study the generation, factors controlling endogenous folate pools, and their functional importance, Friend erythroleukemia cells were grown in media containing 100; 1,000; and 10,000 ng/ml of tritiated pteroylglutamic acid (3H)PteGlu1 and then studied in unlabeled media with varying amounts of PteGlu1. The intracellular folate pool was directly proportional to the PteGlu1 in which the cells were incubated. At equilibrium, greater than 95% of the labeled intracellular folate pool chromatographed as polyglutamyl folate, regardless of the exogenous folate concentration. The functional importance of the intracellular folate pool was studied by varying the endogenous pool and the exogenous (media) supply. The ability of the cells to replicate in the absence of exogenous folate was directly proportional to the intracellular polyglutamyl folate pool. The maximal rate of replication, however, required exogenous PteGlu1 in addition. The cell doubling time was the most important determinant of intracellular folate turnover; changes in the intracellular pool size and the extracellular folate concentration had no effect on the turnover time. In a rapidly proliferating tissue, the onset of functional folate deficiency will be determined by dilution of intracellular polyglutamates among progeny until a critical level is reached.

Animals↗
PubMed1983

Cellular abnormalities of folate deficiency.

To trace the development of folate-deficient abnormalities of morphology and DNA synthesis, Friend erythroleukaemia cells were grown in media containing 10(2), 10(3) and 10(4) ng of [3H]PteGlu1/ml and then transferred to folate-free media. Parameters examined were: intracellular folate levels; growth potential; morphology; dU suppression; and DNA content by flow microfluorimetry. The most sensitive indicators of folate-deficient cell growth were those related to DNA synthesis (dU and flow microfluorimetry). These became abnormal at intracellular folate levels of 0.2-0.5 ng/10(6) cells and markedly so below 0.1 ng/10(6) cells. Morphological criteria were less sensitive. Cells became megaloblastic at intracellular folate levels below 0.06 ng/10(6). The capacity of the cells to replicate in folate-free media was a function of the intracellular folate (ICF): duplications = 4.01 + ln(ICF)/0.67 (r = 0.993, P less than 0.001). These studies demonstrate that regardless of initial intracellular folate levels, cellular stigmata of folate deficiency appear when cellular folate falls below 3 X 10(5) molecules per cell (dU and flow microfluorimetry) and cells lose the capacity for further replication below 7-10 X 10(5) molecules. The intracellular folate level not only predicts early defects, but also determines the replicative capacity.

Cell Division↗
PubMed1982

The role of the enterohepatic cycle in folate supply to tumour in rats.

The importance of the folate enterohepatic cycle in governing the supply of folate to implants of a rapidly-growing tumour were studied in a new animal model. Following enteric administration of tritiated pteroylglutamic acid, [3H]PteGlu1, tumour uptake of labelled folate was limited to CH3[3H]H4PteGlu1 produced by the gut mucosal cells during absorption or subsequently recirculated through the enterohepatic cycle. 50% of the labelled folate reaching the tumour nodules in the first 6 h after enteric administration first circulated through the enterohepatic cycle. In addition, labelled folate taken up by tumour was immediately incorporated into a polyglutamyl folate pool. There was no evidence for a release of labelled folate from tumour for recirculation to the liver. Therefore the liver and folate enterohepatic cycle appear to play a major role in regulating the supply of folate to rapidly proliferating tissues such as tumour by acutely storing folate from the diet and then secreting it into bile for reabsorption and transport to tissue.

Animals↗
PubMed1982

Enterohepatic circulation of methotrexate in rats in vivo.

The pharmacokinetics of the methotrexate enterohepatic cycle were studied in rats in vivo. For plasma levels of methotrexate between 10(-5) and 10(-8) M, biliary levels were directly proportional and concentrated 27-fold. When labeled methotrexate was administered in doses sufficient to achieve plasma levels of 10(-6) M, approximately 50% of methotrexate appeared in the bile in normal animals and up to 80% appeared in anephric animals. In spite of the high percentage of administered methotrexate which appeared in the bile, complete interruption of the enterohepatic cycle in otherwise normal animals did not affect the plasma decay curve of a bolus of methotrexate. The increased biliary excretion which occurred in animals with renal impairment was utilized with possible therapeutic implications. Bile drainage in these animals rapidly decreased plasma methotrexate levels compared to nondrained controls. This suggests that interruption of the methotrexate enterohepatic cycle may provide an alternative for the management of methotrexate toxicity associated with renal insufficiency.

Animals↗
PubMed1980

The effect of trimethoprim/sulfamethoxazole on Friend erythroleukemia cells.

Cultures of Friend erythroleukemia cells were subjected to the antibiotics trimethoprim (T) and sulfamethoxazole (S) at levels equal to or below the usual therapeutic range. At T 8 microgram/ml and S 40 microgram/ml, cell growth was arrested, cells appeared megaloblastic, and the examination of cell-cycle distribution by flow microfluorimetry revealed arrest in S phase. With a tenfold reduction in drug levels (T, 08 microgram/ml; S, 4 microgram/ml) cell growth was less markedly inhibited, morphology remained megaloblastic, and S-phase block was still dramatic. A further tenfold reduction (T, 0.08 microgram/ml; S, 0.4 microgram/ml), well below effective antibacterial levels, allowed normal cell growth and morphology but DNA synthesis was still inhibited. Additions of folinic acid at 100 ng/ml averted all drug effects. Thus T/S can affect cell replication even at levels well below those usually employed and could prolong the rate of recovery of hematopoietic cells in the myelosuppressed patient.

Cell Transformation, Neoplastic↗
PubMed1979

Kinetics of the normal folate enterohepatic cycle.

Detailed studies were undertaken to better define the role of the liver and the folate enterohepatic cycle in folate homeostasis. Three isotopes of folate were employed in a rat model to study several parameters: (a) intestinal transport; (b) variation in hepatic uptake after different routes of administration; (c) hepatic reduction, methylation, and polyglutamate formation; (d) biliary excretion; (e) transport of folate to tissue and its return to liver for re-entry into the enterohepatic cycle. Folate absorption was not affected by the type of folate administered, but subsequent liver accumulation was greater when PteGlu(1) was given rather than CH(3)H(4)PteGlu(1). After liver uptake, CH(3)H(4)PteGlu(1) is rapidly and quantitatively excreted into bile, whereas nonmethylated folates are either methylated and transported into bile or incorporated into a hepatic polyglutamate pool. Bile folate is then reabsorbed for distribution to both tissue and liver, completing the enterohepatic cycle. The importance of this cycle was demonstrated by long-term bile drainage and by transport studies with two isotopes of CH(3)H(4)PteGlu(1). With bile drainage, serum folate levels fell to 30-40% of normal within 6 h, a much more dramatic drop than that seen with folate-free diets alone. Studies with labeled CH(3)H(4)PteGlu(1) demonstrated that about one-third was taken up by tissue, demethylated, and returned to liver for remethylation and recirculation through the bile and gut. This establishes the enterohepatic cycle as a major factor in folate homeostasis and, for the first time, demonstrates a transport pathway between tissue and liver for nonmethylated folate.

Animals↗