Pantothenate kinase (CoaA) is a key regulator of coenzyme A (CoA) biosynthesis in Escherichia coli, and its activity is controlled by feedback inhibition by CoA and its thioesters. The importance of feedback inhibition in the control of the intracellular CoA levels was tested by constructing three site-directed mutants of CoaA that were predicted to be feedback resistant based on the crystal st...

7-Methyltryptophan (7MT) or compounds which can be metabolized to 7MT, 3-methylanthranilic acid (3MA) and 7-methylindole, cause derepression of the trp operon through feedback inhibition of anthranilate synthetase. Tyrosine reverses 3MA or 7-methylindole derepression, apparently by increasing the amount of chorismic acid available to the tryptophan pathway. A mutant isolated on the basis of 3MA...

In neocortex, synaptic inhibition is mediated by gamma-aminobutyric acid-A (GABAA) and GABAB receptors. By using intracellular and patch-clamp recordings in slices of rat visual cortex we studied the balance of excitation and inhibition in different intracortical pathways. The study was focused on the strength of fast GABAA- and slow GABAB-mediated inhibition in interareal forward and feedback ...

Feedback inhibition of gene expression is a widespread phenomenon in which the expression of a gene is downregulated by its protein product. Feedback in eukaryotic cells involves time delays resulting from transcription, transcript splicing and processing, and protein synthesis. In principle, such delays can result in oscillatory mRNA and protein expression. However, experimental evidence of su...

GABAergic feedback inhibition from amacrine cells shapes visual signaling in the inner retina. Rod bipolar cells (RBCs), ON-sensitive cells that depolarize in response to light increments, receive reciprocal GABAergic feedback from A17 amacrine cells and additional GABAergic inputs from other amacrine cells located laterally in the inner plexiform layer. The circuitry and synaptic mechanisms un...

A hierarchy of enzyme-catalyzed positive feedback loops is examined by mathematical and numerical analysis. Four systems are described, from the simplest, in which an enzyme catalyzes its own formation from an inactive precursor, to the most complex, in which two sequential feedback loops act in a cascade. In the latter we also examine the function of a long-range feedback, in which the final e...

Bladder cancer (BC) is the most common urinary system malignancy worldwide. However, molecular mechanisms underlying its progression remain largely unexplored. Accumulating evidence indicates that cancer-associated fibroblasts (CAFs), major constituents of tumor stroma, play a key role in development. Herein, we have successfully isolated CAFs and paired normal (NFs) from bladder tissues. We ob...

conclusions all plants could inhibit mushroom tyrosinase, but more investigations on human tyrosinase and clinical studies are needed. results the hydroalcoholic extract of p. alkekengi showed the most tyrosinase inhibitory effect with ic50 of 0.09 mg/ml vs. 0.38, 0.38 and 2.82 mg/ml of b. persicum, a. rosea and m. vulgare, respectively. m. vulgare exhibited uncompetitive inhibition and other p...

this study aimed at investigating the effect of learners’ gender on their preferences for corrective feedback. learners’ prefer- ences which were investigated included the necessity, frequency, timing, type, method, and delivering agent of error treatment. to this end, a questionnaire was administered to a random sample of 100 participants (50 males and 50 females) studying english (efl) at shi...