The purinergic signalling system is one of the most ancient and arguably the most widespread intercellular signalling system in living tissues. In this review we present a detailed account of the early developments and current status of purinergic signalling. We summarize the current knowledge on purinoceptors, their distribution and role in signal transduction in various tissues in physiological and pathophysiological conditions.

The birth and postnatal development of purinergic signalling

BACKGROUND: Effective upstream preparation of nucleic acid (NA) is important for molecular techniques that detect unique DNA or RNA sequences. The isolated NA should be extracted efficiently and purified away from inhibitors of a downstream molecular assay.

CONTENT: Many NA sample preparation techniques and commercial kits are available. Techniques for cell lysis and isolation or purification of NA were discovered in early NA characterization studies, evolved in the 20th century with molecular techniques, and still serve as the foundation for current methods. Advances in solid phase extraction methods with nonhazardous chemicals and automated systems have changed the way NA is prepared. Factors to consider when selecting NA preparation methods for molecular detection include lysis (from sources as diverse as human cells, viruses, bacterial spores, or protozoan oocysts), DNA vs RNA, sample background, appropriate preparation chemicals, and required detection limits. Methods are also selected on the basis of requirements for a particular application, such as sample volume or removal of inhibitors. Sometimes tradeoffs are made.

SUMMARY: Good automated and manual methods are available to effectively prepare NA for molecular detection in under an hour. Numerous systems are available for various applications, including techniques that are flexible for multiple sample types, are capable of processing large batches, can be performed in <10 min, or that can yield high-purity NA. When methods are selected using the most applicable combination of lysis isolation efficiency and concentration, NA preparation can be very effective, even for molecular detection of multiple targets from the same sample.

http://iacld.ir/DL/elm/94/dnarnapreparationformoleculardetectionreviews.pdf

DNA/RNA Preparation for Molecular Detection

© Springer-Verlag Berlin Heidelberg 2012. All rights are reserved.In the first 20 years that followed the purinergic signalling hypothesis in 1972, most scientists were sceptical about its validity, largely because ATP was so well established as an intracellular molecule involved in cell biochemistry and it seemed unlikely that such a ubiquitous molecule would act as an extracellular signalling molecule. However, after the receptors for ATP and adenosine were cloned and characterized in the early 1990s and ATP was established as a synaptic transmitter in the brain and sympathetic ganglia, the tide turned. More recently it has become clear that ATP is involved in long-term (trophic) signalling in cell proliferation, differentiation and death, in development and regeneration, as well as in short-term signalling in neurotransmission and secretion. Also, important papers have been published showing the molecular structure of P2X receptors in primitive animals like Amoeba and Schistosoma, as well as green algae. This has led to the recognition of the widespread nature of the purinergic signalling system in most cell types and to a rapid expansion of the field, including studies of the pathophysiology as well as physiology and exploration of the therapeutic potential of purinergic agents. In two books, Geoffrey Burnstock and Alexej Verkhratsky have aimed at drawing together the massive and diverse body of literature on purinergic signalling. The topic of this first book is purinergic signalling in the peripheral and central nervous systems and in the individual senses. In a second book the authors focus on purinergic signalling in non-excitable cells, including those of the airways, kidney, pancreas, endocrine glands and blood vessels. Diseases related to these systems are also considered.

Purinergic Signalling and the Nervous System

Histidine is a dietary essential amino acid because it cannot be synthesized in humans. The WHO/FAO requirement for adults for histidine is 10 mg · kg body weight-1 · d-1. Histidine is required for synthesis of proteins. It plays particularly important roles in the active site of enzymes, such as serine proteases (e.g., trypsin) where it is a member of the catalytic triad. Excess histidine may be converted to trans-urocanate by histidine ammonia lyase (histidase) in liver and skin. UV light in skin converts the trans form to cis-urocanate which plays an important protective role in skin. Liver is capable of complete catabolism of histidine by a pathway which requires folic acid for the last step, in which glutamate formiminotransferase converts the intermediate N-formiminoglutamate to glutamate, 5,10 methenyl-tetrahydrofolate, and ammonia. Inborn errors have been recognized in all of the catabolic enzymes of histidine. Histidine is required as a precursor of carnosine in human muscle and parts of the brain where carnosine appears to play an important role as a buffer and antioxidant. It is synthesized in the tissue by carnosine synthase from histidine and β-alanine, at the expense of ATP hydrolysis. Histidine can be decarboxylated to histamine by histidine decarboxylase. This reaction occurs in the enterochromaffin-like cells of the stomach, in the mast cells of the immune system, and in various regions of the brain where histamine may serve as a neurotransmitter.

Mary Ellen Jones

Papers

Albrecht Kossel, A Biographical Sketch