Zonation of forest vegetation and soils of Mount Cameroon,West Africa

Mount Cameroon is an active volcano in a wet part of West Africa. The forest vegetation and associated soils on its southern slopes were studied in 1989, 1991 and 1995 in coupled 0.25 ha plots at altitudes of 180, 600, 1,100, 1,800 and 2,180 m. All lianas and trees >10 cm dbh were enumerated and their structural features quantified. The forests were of large stature throughout. The strangling Schefflera species made a substantial contribution to the very high basal areas at 1,800 m. The associated soils were dominated by andisols derived from volcanic ash that showed a distinct increase with altitude in soil organic matter and total N attributed to lower temperatures. Soil pH, exchangeable K⁺, Ca²⁺, Mg²⁺, effective cation-exchange capacity and percentage base saturation showed very marked increases explained by the influence of recent volcanic ashfalls. Available N and P showed less distinct trends with altitude. Although there is a large decrease in tree species richness with altitude, forest stand growth (as compared on a basal area basis) does not appear to be limited by soil fertility or temperature. The forest line (altitude treeline and extensive gaps below it) appear to be controlled by periodic volcanic activity, ashfalls and lava flows, which can destroy existing forest through soil burial and fire effects and inhibit regrowth on bare lava flows and deep deposits of volcanic ash.     

Neuroprotective effect of small heat shock protein,Hsp27, after acute and chronic alcohol administration

Alcohol induces degeneration of neurons and inhibits neurogenesis in the brain. Small heat shock proteins are able to protect neurons in cerebral ischemia and oxidative stress. In this study, we investigated the neuroprotective effect of small heat shock protein, Hsp27, after acute and chronic ethanol administrations using transgenic mice overexpressing the human Hsp27 protein. Transgenic mice and wild-type littermates were injected with 2 g/kg ethanol intraperitoneally, and then motor coordination and muscle strength were analyzed using different behavioral tests, such as footprint analysis, balance beam, and inverted screen tests. Ethanol-injected transgenic mice showed similar footprints to control saline-injected mice, did not fall of the beam, and were able to climb to the top of the inverted screen, while wild-type mice showed ataxia and incoordination after ethanol injection. The effect of Hsp27 on chronic ethanol consumption was also investigated. Drinking water of mice was replaced by a 20% ethanol solution for 5 weeks, and then brain sections were stained with Fluoro Jade C staining. We found significantly lesser amount of degenerating neurons in the brain of ethanol-drinking transgenic mice compared to wild-type mice. We conclude that Hsp27 can protect neurons against the acute and chronic toxic effects of ethanol.     

Calmodulin: calcium, potassium, and magnesium ion multiple equilibria and kinetics for interconversion, including the effect of repeated stimulation

Using computer simulations, with realistic values for the intrinsic thermodynamic binding constants and kinetic on and off rate constants at the four metal-binding sites, the calmodulin molecule is shown to have been optimally adjusted by evolution for biological function. Despite a very large number of potential molecular states, depending upon occupation by potassium, calcium, or magnesium ions, the system restricts itself to a small number of physiologically-significant equilibrium species. It appears to possess built-in triggers for biological processes, with rapid (approximately 20 ms time-scale), step-function shaped, changes of the populations of the CMKK, CMMK, CKKK, CMMM (and CCKK) states. The time-response of calmodulin to periodic changes in ionic levels (2 and 5 s-1) makes it quite adequate for repeated stimulations. In short, calmodulin appears as a very selective information transmitter at the molecular level.     

The efficacy of the antibacterial peptide,pyrrhocoricin, is finely regulated by its amino acid residues and active domains

Summary Pyrrhocoricin, a highly active antibacterial peptide isolated from insects, inhibits chaperone-assisted protein folding via binding to the 70 kDa heat shock protein DnaK with its amino terminal half. The C-terminus functions as an intracellular delivery module. In the current study, chimeras consisting of the putative functional units of pyrrhocoricin and a related peptide, drosocin, were made, and it was found that some mixed and matched sequences retained their ability to killEscherichia coli, Salmonella typhimurium andAgrobacterium tumefaciens. While pyrrhocoricin appeared to have a more universal pharmacophore, drosocin featured a more robust intracellular delivery unit. We also identified the minimal length of pyrrhocoricin that is needed to efficiently kill bacteria. While for activity againstS. typhimurium the peptide could not be shortened, againstE. coli it was sufficient to have a Vall-Ile16 amino-terminal fragment. Although Vall was not part of the Asp2-Pro 10 pharmacophore (it could be replaced with other residues), it could not be eliminated and apparently played an important role in defining the activity of the peptide. Indeed, when Val1 was replaced with lysine, not only the efficacy of pyrrhocoricin to kill the sensitive strains increased significantly, resulting in the most active antimicrobial peptide against some clinical strains ever made, but the modified peptide was also able to killPseudomonas aeruginosa, an originally unresponsive bacterium in the low μg ml⁻¹ concentration range. However, this substitution likely influenced the interaction with bacterial membranes rather than that with the target protein, and therefore the dominant mode of action of the Lysl-pyrrhocoricin peptide may feature membrane disintegration instead of DnaK inhibition.     

S-methylmethionine alleviates the cold stress by protection of the photosynthetic apparatus and stimulation of the phenylpropanoid pathway

Maize (Zea mays L.) seedlings were pretreated with 0.001 g dm^?3 S-methylmethionine (SMM) in the nutrient solution for 24 h and then subjected to chilling (6 °C for 2, 4, 6, 10, and 24 h). Cold stress significantly decreased the maximum quantum yield of photosystem II (variable to maximum chlorophyll fluorescence ratio, F_v/F_m) during the whole experiment but SMM pretreatment significantly reduced this decline. Content of phenolics and anthocyanins increased in response to low temperature, and SMM pretreatment further intensified the synthesis of these protective agents. These findings were supported by increased expression of genes coding enzymes of the phenylpropanoid pathway leading to synthesis of cinnamate-4-hydroxylase (C4H) and chalcone-synthase (CHS). Our results indicate that SMM pretreatment alleviates the low temperature stress by reducing the damage of the photosynthetic apparatus and stimulating the phenylpropanoid pathway.     

A component of Premarin® enhances multiple cognitive functions and influences nicotinic receptor expression

In women, ovarian hormone loss at menopause has been related to cognitive decline, and some studies suggest that estrogen-containing hormone therapy (HT) can mitigate these effects. Recently, the Women's Health Initiative study found that conjugated equine estrogens, the most commonly prescribed HT, do not benefit cognition. Isolated components of conjugated equine estrogens (tradename Premarin^®) have been evaluated in vitro, with delta^8,9-dehydroestrone (?⁸E1) and equilin showing the strongest neuroprotective profiles. It has not been evaluated whether ?⁸E1 or equilin impact cognition or the cholinergic system, which is affected by other estrogens and known to modulate cognition. Here, in middle-aged, ovariectomized rats, we evaluated the effects of ?⁸E1 and equilin treatments on a cognitive battery and cholinergic nicotinic receptors (nAChR). Specifically, we used ¹²⁵I-labeled epibatidine binding to assay brain nicotinic receptor containing 4α and 2β subunits (α4β2-nAChR), since this nicotinic receptor subtype has been shown previously to be sensitive to other estrogens. ?⁸E1 enhanced spatial working, recent and reference memory. ?⁸E1 also decreased hippocampal and entorhinal cortex α4β2-nAChR expression, which was related to spatial reference memory performance. Equilin treatment did not affect spatial memory or rat α4β2-nAChR expression, and neither estrogen impacted ⁸⁶Rb⁺ efflux, indicating lack of direct action on human α4β2 nAChR function. Both estrogens influenced vaginal smear profiles, uterine weights, and serum luteinizing hormone levels, analogous to classic estrogens. The findings indicate that specific isolated Premarin^® components differ in their ability to affect cognition and nAChR expression. Taken with the works of others showing ?⁸E1-induced benefits on several dimensions of health-related concerns associated with menopause, this body of research identifies ?⁸E1 as a new avenue to be investigated as a potential component of HT that may benefit brain health and function during aging.