Acacia senegal and the gum arabic trade: monograph and annotated bibliography

Increasing population pressures coupled with periodic droughts have brought about deforestation and land degradation in the dry zones of Africa. Without trees, soil fertility declines, and annual grasses and less palatable herbs and shrubs replace the more nutritious perennial species reducing the land productivity. Many exotic tree species have been introduced into sub-Saharan Africa; however they have not proved very successful in the semi-arid areas, where the ravages of droughts, termites and browsing animals drastically reduced their survival. It has now been generally accepted that a solution to combat this decreasing land productivity is to manage and cultivate the indigenous species, particularly the pioneer legumes that are the natural re-colonizers of these disturbed and degraded lands. Prominent among these are the acacias, and for this reason a series of projects was started in 1987 at the Oxford Forestry Institute, funded by the Overseas Development Administration (now Department for International Development) of the Government of the United Kingdom, to explore, assemble and evaluate the genetic resources of the most widespread and economically important African acacias, including Acacia senegal.</p

Acacia senegal and the gum arabic trade: monograph and annotated bibliography

Increasing population pressures coupled with periodic droughts have brought about deforestation and land degradation in the dry zones of Africa. Without trees, soil fertility declines, and annual grasses and less palatable herbs and shrubs replace the more nutritious perennial species reducing the land productivity. Many exotic tree species have been introduced into sub-Saharan Africa; however they have not proved very successful in the semi-arid areas, where the ravages of droughts, termites and browsing animals drastically reduced their survival. It has now been generally accepted that a solution to combat this decreasing land productivity is to manage and cultivate the indigenous species, particularly the pioneer legumes that are the natural re-colonizers of these disturbed and degraded lands. Prominent among these are the acacias, and for this reason a series of projects was started in 1987 at the Oxford Forestry Institute, funded by the Overseas Development Administration (now Department for International Development) of the Government of the United Kingdom, to explore, assemble and evaluate the genetic resources of the most widespread and economically important African acacias, including Acacia senegal.</p

A comparative analysis of the neuroprotective properties of competitive and uncompetitive n-methyl-d-aspartate receptor antagonists in vivo: Implications for the process of excitotoxic degeneration and its therapy

Injection of the N-methyl-d-aspartate receptor agonist, quinolinic acid, into the rat striatum in vivo results in the degeneration of cholinergic and GABAergic neurons, as determined seven days later using the marker enzymes, choline acetyltransferase and glutamate decarboxylase, respectively. Such damage was dose-dependently prevented by CGP 37849 or MK-801 (competitive and uncompetitive N-methyl-d-aspartate receptor antagonists, respectively) administered systemically or intrastriatally at the same time as quinolinic acid.&lt;p&gt;&lt;/p&gt; The neuroprotective activity of CGP 37849 was associated with thed-enantiomer, CGP 40116 (ED507.5 mg/kg i.p.), which was approximately 1.5-fold and 3.5-fold more potent than the related compounds,d-CPPene and CGS 19755, respectively. CGP 37849 was a weaker neuroprotectant than MK-801 (ED500.8mg/kg i.p) when administered systemically, but was dramatically more potent following coinjection with quinolinic acid (Ed50'S 0.2 and 117 nmol, respectively). When injected intrastriatally 0.5–2 h post-quinolinic acid, CGP 37849 was protective over the entire period studied, whereas MK-801 was less effective at all post-quinolinic acid injection times. The finding that CGP 37849 is neuroprotective when administered intrastriatally 1–2 h post-quinolinic acid supports the hypothesis that a period exists following excitotoxic insult in which neurons are not committed to die, and can be rescued by blockade of ongoing. N-methyl-d-aspartate receptor activation.&lt;p&gt;&lt;/p&gt; Competition studies indicated that, when coinjected with 100–400 nmol quinolinic acid into the striatum, CGP 37849 exhibited kinetics predicted of a competitive N-methyl-d-aspartate receptor antagonist (declining neuroprotective potency with increasing doses of agonist), whereas MK-801 displayed a complex picture, with weak protective activity at low doses of quinolinic acid. Following systemic administration, neither antagonist was markedly affected by the dose of excitotoxin. When given i.p. at up to 6 h post-quinolinic acid, CGP 37849 and MK-801 showed essentially identical profiles of post-insult protection; degeneration of cholinergic neurons was reduced significantly throughout the entire post-insult period, whereas GABAergic neurons were protected only when drugs were administered 2 h or earlier post-quinolinic acid.&lt;p&gt;&lt;/p&gt; The data indicate that competitive and uncompetitive N-methyl-d-aspartate receptor antagonists are effective neuroprotectants in vivo, and that parameters such as drug lipophilicity or mechanism of action at the receptor do not impinge upon their properties as systemically active cerebroprotectants.&lt;p&gt;&lt;/p&gt