SUMMARY / RELATED TOPICS

Neurotoxin

Neurotoxins are toxins that are destructive to nerve tissue. Neurotoxins are an extensive class of exogenous chemical neurological insults that can adversely affect function in both developing and mature nervous tissue; the term can be used to classify endogenous compounds, when abnormally contacted, can prove neurologically toxic. Though neurotoxins are neurologically destructive, their ability to target neural components is important in the study of nervous systems. Common examples of neurotoxins include lead, glutamate, nitric oxide, botulinum toxin, tetanus toxin, tetrodotoxin; some substances such as nitric oxide and glutamate are in fact essential for proper function of the body and only exert neurotoxic effects at excessive concentrations. Neurotoxins inhibit neuron control over ion concentrations across the cell membrane, or communication between neurons across a synapse. Local pathology of neurotoxin exposure includes neuron excitotoxicity or apoptosis but can include glial cell damage.

Macroscopic manifestations of neurotoxin exposure can include widespread central nervous system damage such as intellectual disability, persistent memory impairments and dementia. Additionally, neurotoxin-mediated peripheral nervous system damage such as neuropathy or myopathy is common. Support has been shown for a number of treatments aimed at attenuating neurotoxin-mediated injury, such as antioxidant and antitoxin administration. Exposure to neurotoxins in society is not new, as civilizations have been exposed to neurologically destructive compounds for thousands of years. One notable example is the possible significant lead exposure during the Roman Empire resulting from the development of extensive plumbing networks and the habit of boiling vinegared wine in lead pans to sweeten it, the process generating lead acetate, known as "sugar of lead". In part, neurotoxins have been part of human history because of the fragile and susceptible nature of the nervous system, making it prone to disruption.

The nervous tissue found in the brain, spinal cord, periphery comprises an extraordinarily complex biological system that defines many of the unique traits of individuals. As with any complex system, however small perturbations to its environment can lead to significant functional disruptions. Properties leading to the susceptibility of nervous tissue include a high surface area of neurons, a high lipid content which retains lipophilic toxins, high blood flow to the brain inducing increased effective toxin exposure, the persistence of neurons through an individual's lifetime, leading to compounding of damages; as a result, the nervous system has a number of mechanisms designed to protect it from internal and external assaults, including the blood brain barrier. The blood-brain barrier is one critical example of protection which prevents toxins and other adverse compounds from reaching the brain; as the brain requires nutrient entry and waste removal, it is perfused by blood flow. Blood can carry a number of ingested toxins, which would induce significant neuron death if they reach nervous tissue.

Thus, protective cells termed astrocytes surround the capillaries in the brain and absorb nutrients from the blood and subsequently transport them to the neurons isolating the brain from a number of potential chemical insults. This barrier creates a tight hydrophobic layer around the capillaries in the brain, inhibiting the transport of large or hydrophilic compounds. In addition to the BBB, the choroid plexus provides a layer of protection against toxin absorption in the brain; the choroid plexuses are vascularized layers of tissue found in the third and lateral ventricles of the brain, which through the function of their ependymal cells, are responsible for the synthesis of cerebrospinal fluid. Through selective passage of ions and nutrients and trapping heavy metals such as lead, the choroid plexuses maintain a regulated environment which contains the brain and spinal cord. By being hydrophobic and small, or inhibiting astrocyte function, some compounds including certain neurotoxins are able to penetrate into the brain and induce significant damage.

In modern times and physicians have been presented with the challenge of identifying and treating neurotoxins, which has resulted in a growing interest in both neurotoxicology research and clinical studies. Though clinical neurotoxicology is a burgeoning field, extensive inroads have been made in the identification of many environmental neurotoxins leading to the classification of 750 to 1000 known neurotoxic compounds. Due to the critical importance of finding neurotoxins in common environments, specific protocols have been developed by the United States Environmental Protection Agency for testing and determining neurotoxic effects of compounds. Additionally, in vitro systems have increased in use as they provide significant improvements over the more common in vivo systems of the past. Examples of improvements include tractable, uniform environments, the elimination of contaminating effects of systemic metabolism. In vitro systems, have presented problems as it has been difficult to properly replicate the complexities of the nervous system, such as the interactions between supporting astrocytes and neurons in creating the BBB.

To further complicate the process of determining neurotoxins when testing in-vitro and cytotoxicity may be difficult to distinguish as exposing neurons directly to compounds may not be possible in-vivo, as it is in-vitro. Additionally, the response of cells to chemicals may not convey a distinction between neurotoxins and

Paspalum dilatatum

Paspalum dilatatum is a species of grass known by the common name dallisgrass, Dallas grass, or sticky heads. It is native to Brazil and Argentina, but it is known throughout the world as an introduced species and at times a common weed, its rapid growth and spreading rhizomes make it an invasive pest in some areas. It is present in the southern half of North America, southern Europe, much of Africa, New Zealand, many tropical and subtropical areas. Paspalum dilatatum is a food source including the long-tailed widowbird; the common name dallisgrass was derived from T. A. Dallis, a 19th-century farmer who grew the species extensively near La Grange, Georgia; this is a perennial bunch grass spreading outward. It grows erect to well over 1 m tall; the leaves are hairless, growing up to 35 cm long and one wide. The inflorescence is divided into a few branches lined neatly with beadlike pairs of green to purple spikelets. {https://projects.ncsu.edu/forage/dallis.htm "Paspalum dilatatum". Germplasm Resources Information Network.

Agricultural Research Service, United States Department of Agriculture. Jepson Manual Treatment Grass Manual Treatment Photo gallery

Giovanni Gallini

Giovanni Andrea Battista Gallini known as Sir John Andrew Gallini, was an Italian dancer and impresario, made a "Knight of the Golden Spur" by the Pope following a successful performance. He was the grandson of Domenico Gallini, his father was Luca Gallini and his mother was Maria Umilta Agostini, the daughter of Giovanni Agostini. Gallini was trained in Paris by François Marcel and emigrated to England at an unknown date, though he had been performing at the Académie Royale de Musique. By 17 December 1757 he was dancing at Covent Garden Theatre. Between 1758 and 1766 he performed and served as director of dances at the King's Theatre now Her Majesty's Theatre, except for an interval at Covent Garden in late 1763 and 1764, he ceased to perform in public at the end of the 1766 season. In a campaign to raise the intellectual respectability of dance, on 3 March 1762 Gallini published A Treatise on the Art of Dancing, followed by Critical Observations on the Art of Dancing. Dance historians agree that these elegantly printed volumes were derivative, citing Weaver and other sources, but were important statements of philosophy that helped gain Gallini entrée into society.

While teaching dance, at which he was expert, he courted and married on 23 February 1763 at St James's, Lady Elizabeth Peregrine Bertie, the daughter of Willoughby Bertie, 3rd Earl of Abingdon. She gave birth to twin sons Francis Cecil Gallini and John Andrea Gallini on 13 October 1766 and to two daughters, Joyce Ann Gallini and Louise Gallini. Notwithstanding outrage in parts of the fashionable world, her family accepted the match. However, the marriage broke down, in years the couple lived apart. In 1766, Norreys Bertie left his estates to Elizabeth's brother Captain Peregrine, charging Hampstead Norreys with an annuity to Elizabeth. Willoughby Bertie, 4th Earl of Abingdon, was a music patron and composer, as well as a political writer and his brother-in-law. Gallini brought Bertie into contact with J. C. Bach and Carl Friedrich Abel, he was subsequently involved in their careers. Gallini was a friend of Haydn's. Haydn went to Vienna, there he was found by Johann Peter Salomon, the great German-born violinist and impresario who had settled in London, where he gave successful subscription concerts.

Salomon had read of Prince Esterházy's death while recruiting singers in Cologne and had hastened to Vienna to engage Haydn, if possible Mozart as well. Salomon was a brilliant businessman and his proposal to Haydn was so attractive that the composer could hardly refuse: 3000 gulden from the great impresario Gallini, director of the King's Theatre in the Haymarket, for a new opera and 100 gulden for each of twenty new instrumental or vocal pieces to be conducted by Haydn in Salomon's subscription concerts; as soon as Haydn set foot on English soil, 5000 gulden were to be deposited in Haydn's Viennese bank, Fries & Co. In addition to the money and property his wife brought him, famously parsimonious, accumulated a substantial fortune. On 28 June 1774, with Johann Christian Bach and Carl Friedrich Abel, he purchased premises in Hanover Square, where the three men built a splendid concert hall—the Hanover Square Rooms—95 feet by 30. Gallini bought out his partners on 12 November 1776 and continued to operate the hall for the rest of his life, making large sums from series such as the Professional Concert and Academy of Ancient Music, from masquerades held there.

Not content, in the spring of 1778 Gallini attempted to buy the opera at the King's Theatre, Haymarket. Xenophobia against him coalesced into a bidding war won by Richard Brinsley Sheridan and Thomas Harris, who paid the outlandish price of £22,000 for the enterprise. Unfamiliar with opera, they began losing large sums. After seven years of transfers of authority, forced declarations of bankruptcy, feuding trustees, sheriff's sales, he achieved his wish, though the conditions were far from ideal, he served as trustee for William Taylor, who loathed him, harassed him, sued him year after year, he had to operate under a budget cap of £18,000 enforced by the court of chancery. The lord chamberlain, who regarded him as an undesirable foreigner, made him struggle to get a licence to perform. Gallini paid more attention to opera than to dance, mounting creditable seasons. To supplement the Italian repertory he began to import both works and performers from German houses, he drew to England such major performers as Gertrud Elisabeth Mara and the castratos, Giovanni Maria Rubinelli and Luigi Marchesi.

Dance required more than a single star, however. Without a major choreographer Auguste Vestris's performance seemed less brilliant, although Jean-Georges Noverre returned at the end of 1787 the talent provided for him to work with was so limited that in February 1789 a riotous audience demanded that better dancers be imported. After Marie-Madeleine Guimard consented to a short visit for exorbitant fees, Gallini somehow managed to run up a profit of £4000 in four seasons—though the money went to the theatre's innumerable creditors. All along, rent from concerts continued to increase Gallini's personal fortune. In 1784, Gallini and Elizabeth bought the manors of Hampstead Norreys and Bothampstead from her brother Peregrine, followed in 1785 by the adjacent manor of Yattendon, he acquired real estate abr