Peritoxins and their effects on sorghum

1995 ◽  
Vol 73 (S1) ◽  
pp. 444-452 ◽  
Author(s):  
Larry D. Dunkle ◽  
Vlado Macko
Keyword(s):  
Root Rot ◽  
Signal Transduction Pathway ◽  
Normal Function ◽  
Disease Symptoms ◽  
Kinase C ◽  
Protein Kinase C Activity ◽  
Primary Roots ◽  
Low Concentrations ◽  
Enhanced Expression ◽  
Periconia Circinata

Peritoxins are low molecular weight, chlorinated peptides produced only by pathogenic strains of the sorghum root rot fungus, Periconia circinata. Genetic data relating sensitivity of sorghum (Sorghum bicolor (L.) Moench) to these toxins and susceptibility to the pathogen are consistent with the hypothesis that both traits are controlled by a single semidominant gene (Pc). At low concentrations (5–500 nM), the toxin selectively reproduces disease symptoms, inhibits growth of primary roots, stops mitosis, induces electrolyte leakage, and enhances the synthesis of a group of 16-kDa proteins and the corresponding mRNAs. Enhanced expression of these 16-kDa proteins and disease symptoms are also induced in a nongenotype-specific manner by treatment with mercury, suggesting that the two events are causally related. However, the upregulation of 16-kDa protein expression induced by a fungal elicitor is independent of visible disease symptoms and is, therefore, not a direct cause of damage. Results of experiments with treatments that protect seedlings against the effects of toxin (e.g., proteinase, heat shock, inhibitors of protein or RNA synthesis, inhibitors of protein kinase C activity, and biotinylation of membrane proteins) suggest that disease symptoms result from an interaction of peritoxin with a proteinaceous receptor on or near the cell surface and interference with the normal function of a signal transduction pathway. Key words: peritoxin, sorghum, Periconia circinata, host-selective toxin, milo disease, Periconia root rot.

Stimulus-secretion coupling in parathyroid cells deficient in protein kinase C activity

1994 ◽  
Vol 267 (3) ◽  
pp. E429-E438
Author(s):  
F. K. Racke ◽  
E. F. Nemeth
Keyword(s):  
Protein Kinase C ◽  
Parathyroid Hormone ◽  
Protein Kinase ◽  
Kinase C ◽  
Protein Kinase C Activity ◽  
Low Concentrations ◽  
Stimulus Secretion Coupling ◽  
Subsequent Addition ◽  
In Cells

The role of protein kinase C (PKC) in regulating cytosolic Ca2+ concentrations ([Ca2+]i) and parathyroid hormone (PTH) secretion was studied in bovine parathyroid cells rendered deficient in PKC activity by incubation with phorbol 12-myristate 13-acetate (PMA). Pretreatment with PMA caused a time- and concentration-dependent loss of functional PKC activity as assessed by the failure of [Ca2+]i and PTH secretion to respond to the subsequent addition of PKC activators or the inhibitor staurosporine. Pretreatment for 24 h with 1 microM PMA caused a loss of 85% of the total and 98% of the cytosolic PKC activity. Cells so pretreated were considered to be "PKC downregulated." Increasing the concentration of extracellular Ca2+ or Mg2+ caused corresponding increases in [Ca2+]i that were similar in control and in PKC-downregulated cells. PTH secretion regulated by extracellular Ca2+ or Mg2+ was likewise similar in control and PKC-downregulated cells. Stimulus-secretion coupling is thus unimpaired in parathyroid cells deficient in PKC activity. Cytosolic Ca2+ responses remained depressed in cells incubated for 24 h with low concentrations of PMA (30 or 100 nM). However, under these conditions, extracellular Ca2+ still suppressed PTH secretion similarly to control cells. These results reveal a dissociation between cytosolic Ca2+ and PTH secretion and suggest that signals other than cytosolic Ca2+ are involved in the regulation of PTH secretion.

Chronic treatment by the calcium channel blocker ± PN 200-110 in the rat counteracts the stimulations of pituitary weight, prolactin release and pituitary C-kinase activity induced by a chronic estradiol treatment, in vivo

1990 ◽  
Vol 122 (3) ◽  
pp. 403-408
Author(s):  
Ph. Touraine ◽  
P. Birman ◽  
F. Bai-Grenier ◽  
C. Dubray ◽  
F. Peillon ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Calcium Channel ◽  
Calcium Channel Blocker ◽  
Channel Blocker ◽  
Plasma Prolactin ◽  
Estradiol Treatment ◽  
Kinase C ◽  
Protein Kinase C Activity

Abstract In order to investigate whether a calcium channel blocker could modulate the protein kinase C activity in normal and estradiol pretreated rat pituitary, female Wistar rats were treated or not (controls) with ± PN 200-110 (3 mg · kg−1 · day−1, sc) for 8 days or with estradiol cervical implants for 8 or 15 days, alone or in combination with PN 200-110 the last 8 days. Estradiol treatment induced a significant increase in plasma prolactin levels and pituitary weight. PN 200-110 administered to normal rats did not modify these parameters, whereas it reduced the effects of the 15 days estradiol treatment on prolactin levels (53.1 ± 4.9 vs 95.0 ±9.1 μg/l, p<0.0001) and pituitary weight (19.9 ± 0.4 vs 23.0 ± 0.6 mg, p <0.001), to values statistically comparable to those measured after 8 days of estradiol treatment. PN 200-110 alone did not induce any change in protein kinase C activity as compared with controls. In contrast, PN 200-110 treatment significantly counteracted the large increase in soluble activity and the decrease in the particulate one induced by estradiol between day 8 and day 15. We conclude that PN 200-110 opposed the stimulatory effects of chronic in vivo estradiol treatment on plasma prolactin levels and pituitary weight and that this regulation was related to a concomitant modulation of the protein kinase C activity.

Swainsonine Modulation of Protein Kinase C Activity in Murine Peritoneal Macrophages

1990 ◽  
Vol 2 (10) ◽  
pp. 333-338 ◽  
Author(s):  
Pascal Breton ◽  
Amha Asseffa ◽  
Krzysztof Grzegorzewski ◽  
Steven K. Akiyama ◽  
Sandra L. White ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Peritoneal Macrophages ◽  
Kinase C ◽  
Protein Kinase C Activity ◽  
Murine Peritoneal Macrophages

Uncertainties Associated with Assessing the Risk of an Endocrine Active Substance in the Canadian Environment

2001 ◽  
Vol 36 (2) ◽  
pp. 319-330 ◽  
Author(s):  
Mark Servos ◽  
Don Bennie ◽  
Kent Burnison ◽  
Philippa Cureton ◽  
Nicol Davidson ◽  
...  
Keyword(s):  
Risk Assessment ◽  
Endocrine Disruption ◽  
Endocrine System ◽  
Problem Formulation ◽  
Normal Function ◽  
Weight Of Evidence ◽  
Biological Responses ◽  
Low Concentrations ◽  
Multigenerational Effects

Abstract A number of biological responses and multigenerational effects, mediated through the disruption of endocrine systems, have been observed in biota exposed to relatively low concentrations of environmental contaminants. These types of responses need to be considered within a weight of evidence approach in our risk assessment and risk management frameworks. However, including endocrine responses in an environmental risk assessment introduces a number of uncertainties that must be considered. A risk assessment of nonylphenol and nonylphenol polyethoxylates (NP/NPE) is used as a case study to demonstrate the sources and magnitude of some of the uncertainties associated with using endocrine disruption as an assessment endpoint. Even with this relatively well studied group of substances, there are substantial knowledge gaps which contribute to the overall uncertainties, limiting the interpretation within the risk assessment. The uncertainty of extrapolating from in vitro or biochemical responses to higher levels of organization or across species is not well understood. The endocrine system is very complex and chemicals can interact or interfere with the normal function of endocrine systems in a number of ways (e.g., receptors, hormones) which may or may not result in an adverse responses in the whole organism. Using endocrine responses can lead to different conclusions than traditional endpoints due to a variety of factors, such as differences in relative potencies of chemicals for specific endpoints (e.g., receptor binding versus chronic toxicity). The uncertainties can also be considerably larger and the desirability of using endocrine endpoints should be carefully evaluated. Endocrine disruption is a mode of action and not a functional endpoint and this needs to be considered carefully in the problem formulation stage and the interpretation of the weight of evidence.

scholarly journals Stimulus-response coupling in insulin-secreting HIT cells. Effects of secretagogues on cytosolic Ca2+, diacylglycerol, and protein kinase C activity.

1990 ◽  
Vol 265 (25) ◽  
pp. 15003-15009 ◽  
Author(s):  
R. Regazzi ◽  
G.D. Li ◽  
J. Deshusses ◽  
C.B. Wollheim
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Stimulus Response ◽  
Kinase C ◽  
Protein Kinase C Activity ◽  
Hit Cells

Effect of phorbol myristate acetate on secretion of parathyroid hormone

1988 ◽  
Vol 254 (1) ◽  
pp. E63-E70 ◽  
Author(s):  
J. J. Morrissey
Keyword(s):  
Protein Kinase C ◽  
Parathyroid Hormone ◽  
Protein Kinase ◽  
Membrane Fraction ◽  
Hormone Secretion ◽  
Myristate Acetate ◽  
Kinase C ◽  
Low Calcium ◽  
Protein Kinase C Activity ◽  
High Calcium

The influence of phorbol myristate acetate (PMA), an activator of protein kinase c, on the secretion of parathyroid hormone from collagenase-dispersed bovine parathyroid cells was tested. The cells were incubated at low (0.5 mM) or high (2.0 mM) concentrations of calcium in the medium, and the hormone secreted into the medium was measured by a radioimmunoassay that recognizes both intact and C-terminal fragments of hormone. At low calcium, the secretory rate averaged 32 +/- 3.8 ng.h-1.(10(5) cells)-1. The addition of 1.6 microM PMA did not affect secretion. At high calcium there was a significant suppression of secretion by 38% to 19.8 +/- 3 ng.h-1.(10(5) cells)-1. The addition of 1.6 microM PMA significantly stimulated hormone secretion to 35.8 +/- 8 ng.h-1.(10(5) cells)-1, a rate indistinguishable from low calcium. This stimulatory effect of PMA at high calcium was seen at PMA concentrations as low as 1.6 nM, did not occur with a biologically inactive 4 alpha-isomer of phorbol ester, and was independent of changes in cellular adenosine 3',5'-cyclic monophosphate levels. Examination of 32P-labeled phosphoproteins by two-dimensional gel electrophoresis revealed acidic proteins of approximately 20,000 and 100,000 Da that were phosphorylated at low and high calcium + 1.6 microM PMA but not at high calcium alone. The protein kinase c activity associated with the membrane fraction of parathyroid cells significantly decreased 40% when the cells were incubated at high vs. low calcium. The data suggest that calcium may regulate parathyroid hormone secretion through changes in protein kinase c activity of the membrane fraction of the cell and protein phosphorylation.

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