A catabolite-resistance mutation is localized in the rpo operon of Bacillus subtilis

1984 ◽  
Vol 30 (4) ◽  
pp. 423-429 ◽  
Author(s):  
Dongxu Sun ◽  
I. Takahashi
Keyword(s):  
Bacillus Subtilis ◽  
Rna Polymerase ◽  
Partial Resistance ◽  
Carbon Sources ◽  
Resistance Mutation ◽  
Inhibitory Effect ◽  
High Concentrations

By transformation analysis, a mutation (crsE1), which makes Bacillus subtilis cells able to sporulate in the presence of relatively high concentrations of glucose and other carbon sources, was mapped in the rpoBC operon. The effect of crsE1 mutation can be suppressed by another mutation in the same operon, rfm11, which confers resistance to rifamycin. Mutants carrying stv or std mutations, which are also located in the rpoBC operon, showed partial resistance to catabolites in sporulation. It appears therefore that a change in the structure or synthesis of RNA polymerase may alter the response of cells to the inhibitory effect of catabolites on sporulation.

Genetic mapping of catabolite-resistant mutants of Bacillus subtilis

1982 ◽  
Vol 28 (11) ◽  
pp. 1242-1251 ◽  
Author(s):  
Dongxu Sun ◽  
I. Takahashi
Keyword(s):  
Bacillus Subtilis ◽  
Genetic Mapping ◽  
Carbon Sources ◽  
Resistance Mutations ◽  
Resistant Mutants ◽  
High Concentrations

Using mutants of Bacillus subtilis that are able to sporulate in the presence of relatively high concentrations of various carbon sources, catabolite resistance mutations were mapped by PBS1 transduction and transformation. Catabolite resistance mutations were localized at six different loci on the chromosome of B. subtilis. The map positions of our mutants suggest that they are distinct from sacUh, catA, and scoC reported by other investigators. Relations between our findings and initiation of sporulation have been discussed.

Effects of various inhibitory agents on sporulation of Bacillus subtilis

1982 ◽  
Vol 28 (1) ◽  
pp. 80-86 ◽  
Author(s):  
I. Takahashi ◽  
L. W. MacKenzie
Keyword(s):  
Bacillus Subtilis ◽  
Acridine Orange ◽  
Nalidixic Acid ◽  
Exponential Growth ◽  
Morphological Changes ◽  
Carbon Sources ◽  
Stage Iv ◽  
Electron Microscopic ◽  
High Concentrations ◽  
Inhibitory Agents

Electron microscopic examinations of Bacillus subtilis cells revealed that relatively high concentrations of carbon sources blocked sporulation at stage 0 in most cells. Both nalidixic acid and novobiocin blocked sporulation at stage 0. The cells treated with acridine orange showed the morphology of stage IV 5 h after the end of exponential growth, but no further progression was observed. Mutants that are able to sporulate in the presence of these agents had the characteristic morphological changes observed in uninhibited cultures.

In Vitro Effects of Ethanol on Rabbit Platelet Aggregation, Secretion of Granule Contents, and Cyclic AMP Levels in the Presence of Prostacyclin

1989 ◽  
Vol 61 (02) ◽  
pp. 254-258 ◽  
Author(s):  
Margaret L Rand ◽  
Peter L Gross ◽  
Donna M Jakowec ◽  
Marian A Packham ◽  
J Fraser Mustard
Keyword(s):  
Cyclic Amp ◽  
Inhibitory Effect ◽  
Rabbit Platelet ◽  
Inhibitory Effects ◽  
Low Concentrations ◽  
Rabbit Platelets ◽  
High Concentrations ◽  
In Vitro Effects ◽  
Aggregation Of Platelets

SummaryEthanol, at physiologically tolerable concentrations, inhibits platelet responses to low concentrations of collagen or thrombin, but does not inhibit responses of washed rabbit platelets stimulated with high concentrations of ADP, collagen, or thrombin. However, when platelet responses to high concentrations of collagen or thrombin had been partially inhibited by prostacyclin (PGI2), ethanol had additional inhibitory effects on aggregation and secretion. These effects were also observed with aspirin- treated platelets stimulated with thrombin. Ethanol had no further inhibitory effect on aggregation of platelets stimulated with ADP, or the combination of ADP and epinephrine. Thus, the inhibitory effects of ethanol on platelet responses in the presence of PGI2 were very similar to its inhibitory effects in the absence of PGI2, when platelets were stimulated with lower concentrations of collagen or thrombin. Ethanol did not appear to exert its inhibitory effects by increasing cyclic AMP above basal levels and the additional inhibitory effects of ethanol in the presence of PGI2 did not appear to be brought about by further increases in platelet cyclic AMP levels.

Inhibition of Platelet Function by Antiarrhythmic Drugs, Verapamil and Disopyramide

1982 ◽  
Vol 47 (02) ◽  
pp. 150-153 ◽  
Author(s):  
P Han ◽  
C Boatwright ◽  
N G Ardlie
Keyword(s):  
Platelet Aggregation ◽  
Platelet Function ◽  
Antiarrhythmic Drugs ◽  
Adenosine Diphosphate ◽  
Inhibitory Effect ◽  
Second Phase ◽  
Ionophore A23187 ◽  
High Concentrations ◽  
Artery Disease

SummaryVarious cardiovascular drugs such as nitrates and propranolol, used in the treatment of coronary artery disease have been shown to have an antiplatelet effect. We have studied the in vitro effects of two antiarrhythmic drugs, verapamil and disopyramide, and have shown their inhibitory effect on platelet function. Verapamil, a calcium channel blocker, inhibited the second phase of platelet aggregation induced by adenosine diphosphate (ADP) and inhibited aggregation induced by collagen. Disopyramide similarly inhibited the second phase of platelet aggregation caused by ADP and aggregation induced by collagen. Either drug in synergism with propranolol inhibited ADP or collagen-induced platelet aggregation. Disopyramide at high concentrations inhibited arachidonic add whereas verapamil was without effect. Verapamil, but not disopyramide, inhibited aggregation induced by the ionophore A23187.

Functional Involvement of Thrombospondin in Platelet Aggregation Induced by Low Versus High Concentrations of Thrombin

1986 ◽  
Vol 55 (01) ◽  
pp. 136-142 ◽  
Author(s):  
K J Kao ◽  
David M Shaut ◽  
Paul A Klein
Keyword(s):  
Platelet Aggregation ◽  
Binding Sites ◽  
Inhibitory Effect ◽  
Activated Platelets ◽  
Low Concentrations ◽  
Platelet Binding ◽  
Functional Involvement ◽  
Thrombin Activation ◽  
Platelet Aggregates ◽  
High Concentrations

SummaryThrombospondin (TSP) is a major platelet secretory glycoprotein. Earlier studies of various investigators demonstrated that TSP is the endogenous platelet lectin and is responsible for the hemagglutinating activity expressed on formaldehyde-fixed thrombin-treated platelets. The direct effect of highly purified TSP on thrombin-induced platelet aggregation was studied. It was observed that aggregation of gel-filtered platelets induced by low concentrations of thrombin (≤0.05 U/ml) was progressively inhibited by increasing concentrations of exogenous TSP (≥60 μg/ml). However, inhibition of platelet aggregation by TSP was not observed when higher than 0.1 U/ml thrombin was used to activate platelets. To exclude the possibility that TSP inhibits platelet aggregation by affecting thrombin activation of platelets, three different approaches were utilized. First, by using a chromogenic substrate assay it was shown that TSP does not inhibit the proteolytic activity of thrombin. Second, thromboxane B2 synthesis by thrombin-stimulated platelets was not affected by exogenous TSP. Finally, electron microscopy of thrombin-induced platelet aggregates showed that platelets were activated by thrombin regardless of the presence or absence of exogenous TSP. The results indicate that high concentrations of exogenous TSP (≥60 μg/ml) directly interfere with interplatelet recognition among thrombin-activated platelets. This inhibitory effect of TSP can be neutralized by anti-TSP Fab. In addition, anti-TSP Fab directly inhibits platelet aggregation induced by a low (0.02 U/ml) but not by a high (0.1 U/ml) concentration of thrombin. In conclusion, our findings demonstrate that TSP is functionally important for platelet aggregation induced by low (≤0.05 U/ml) but not high (≥0.1 U/ml) concentrations of thrombin. High concentrations of exogenous TSP may univalently saturate all its platelet binding sites consequently interfering with TSP-crosslinking of thrombin-activated platelets.

Sign in / Sign up

Export Citation Format

Share Document