Genotype frequencies of polymorphic GSTM1, GSTT1, and cytochrome P450 CYP1A1 in Mexicans

The genotype frequencies of three metabolic polymorphisms were determined in a sample of a typical community in central Mexico. CYP1A1*3, GSTM1, and GSTT1 polymorphisms were studied in 150 donors born in Mexico and with Mexican ascendants; with respect to ethnicity the subjects can be considered Mestizos. PCR reactions were used to amplify specific fragments of the selected genes from genomic DNA. An unexpected 56.7% frequency of the CYP1A1*3 allele (which depends on the presence of a Val residue in the 462 position of the enzyme, instead of Ile) was found, the highest described for open populations of different ethnic origins (i.e., Caucasian, Asian, African, or African American). The GSTM1 null genotype was found with a frequency of 42.6%, which is not different from other ethnicities, whereas the GSTT1 null genotype had a frequency of 9.3%, one of the lowest described for any ethnic group but comparable to the frequency found in India (9.7%). The frequency of the combined genotype CYP1A1*3/*3 and the GSTM1 null allele is one of the highest observed to date (or perhaps the highest): 13.7% among all the ethnicities studied, including Caucasians and Asians, whereas the combination of CYP1A1*3/*3 with the GSTT1 null allele reached only 2.8%. The GSTM1 null allele combined with the GSTT1 null allele, on the other hand, has one of the lowest frequencies described, 4.24%, comparable to the frequencies found in African Americans and Indians. Finally, the combined CYP1A1*3/*3, GSTM1 null allele, and GSTT1 null allele genotype could not be found in the sample studied; it is assumed that the frequency of carriers of these combined genotypes is less than 1%. CYP1A1*3 and CYP1A1*2 polymorphisms were also evaluated in 50 residents in a community of northern Mexico; the CYP1A1*3 frequency was 54%, similar to that found in the other community studied, and the CYP1A1*2 frequency was 40%, which is high compared to Caucasians and Asians but comparable to the frequency found in Japanese and lower than the frequency found in Mapuche Indians. Haplotype frequencies for these CYP1A1 polymorphisms were estimated, and a linkage disequilibrium value (D) of 0.137 was calculated.     

PI3 kinase/Akt activation mediates estrogen and IGF-1 nigral DA neuronal neuroprotection against a unilateral rat model of Parkinson's disease

Recently, using the medial forebrain bundle (MFB) 6-hydroxydopmaine (6-OHDA) lesion rat model of Parkinson's disease (PD), we have demonstrated that blockade of central IGF-1 receptors (IGF-1R) attenuated estrogen neuroprotection of substantia nigra pars compacta (SNpc) DA neurons, but exacerbated 6-OHDA lesions in IGF-1 only treated rats (Quesada and Micevych [2004]: J Neurosci Res 75:107-116). This suggested that the IGF-1 system is a central mechanism through which estrogen acts to protect the nigrostriatal DA system. Moreover, these results also suggest that IGF-1R-induced intracellular signaling pathways are involved in the estrogen mechanism that promotes neuronal survival. In vitro, two convergent intracellular signaling pathways used by estrogen and IGF-1, the mitogen-activated protein kinase (MAPK/ERK), and phosphatidyl-inositol-3-kinase/Akt (PI3K/Akt), have been demonstrated to be neuroprotective. Continuous central infusions of MAPK/ERK and PI3K/Akt inhibitors were used to test the hypothesis that one or both of these signal transduction pathways mediates estrogen and/or IGF-1 neuroprotection of SNpc DA neurons after a unilateral administration of 6-OHDA into the MFB of rats. Motor behavior tests and tyrosine hydroxylase immunoreactivity revealed that the inhibitor of the PI3K/Akt pathway (LY294002) blocked the survival effects of both estrogen and IGF-1, while an inhibitor of the MAPK/ERK signaling (PD98059) was ineffective. Western blot analyses showed that estrogen and IGF-1 treatments increased PI3K/Akt activation in the SN; however, MAPK/ERK activation was decreased in the SN. Indeed, continuous infusions of inhibitors blocked phosphorylation of PI3K/Akt and MAPK/ERK. These findings indicate that estrogen and IGF-1-mediated SNpc DA neuronal protection is dependent on PI3K/Akt signaling, but not on the MAPK/ERK pathway.     

Copper increases the damage to DNA and proteins caused by reactive oxygen species

Copper [Cu(II)] is an ubiquitous transition and trace element in living organisms. It increases reactive oxygen species (ROS) and free-radical generation that might damage biomolecules like DNA, proteins, and lipids. Furthermore, ability of Cu(II) greatly increases in the presence of oxidants. ROS, like hydroxyl (·OH) and superoxide (·O₂) radicals, alter both the structure of the DNA double helix and the nitrogen bases, resulting in mutations like the AT→GC and GC→AT transitions. Proteins, on the other hand, suffer irreversible oxidations and loss in their biological role. Thus, the aim of this investigation is to characterize, in vitro, the structural effects caused by ROS and Cu(II) on bacteriophage λ DNA or proteins using either hydrogen peroxide (H₂O₂) or ascorbic acid with or without Cu(II). Exposure of DNA to ROS-generating mixtures results in electrophoretic (DNA breaks), spectrophotometric (band broadening, hypochromic, hyperchromic, and bathochromic effects), and calorimetric (denaturation temperature [T _d], denaturation enthalpy [ΔH], and heat capacity [C _p] values) changes. As for proteins, ROS increased their thermal stability. However, the extent of the observed changes in DNA and proteins were distinct, depending on the efficiency of the systems assayed to generate ROS. The resulting effects were most evident when Cu(II) was present. In summary, these results show that the ROS, ·O₂ and ·OH radicals, generated by the Cu(II) systems assayed deeply altered the chemical structure of both DNA and proteins. The physiological relevance of these structural effects should be further investigated.     

Microsomal Transformation of Organophosphorus Pesticides by White Rot Fungi

The enzymatic mechanism for the transformationof organophosphorus pesticides (OPPs) by differentwhite-rot fungi strains was studied. With theexception of Ganoderma applanatum 8168,all strains from a collection of 17 different fungicultures were able to deplete parathion. Threestrains showing the highest activities were selectedfor further studies: Bjerkandera adusta 8258,Pleurotus ostreatus 7989 and Phanerochaetechrysosporium 3641. These strains depleted 50 to96% of terbufos, azinphos-methyl, phosmet andtribufos after four-days exposure to the pesticides.In order to identify the cellular localization of thetransformation activity, the extracellular andmicrosomal fractions of Pleurotus ostreatus7989 were evaluated in vitro. While the activitiesof ligninolytic enzymes (lignin peroxidase,manganese peroxidase and laccase) weredetected in the extracellular fraction, noenzymatic modification of any of the fivepesticides tested could be found, suggestingthe intracellular origin of the transformationactivity. In accordance with this observation themicrosomal fraction was found able to transformthree OPPs with the following rates:10 mol mg prot^-1 h^-1 forphosmet, 5.7 mol mg prot^-1 h^-1 forterbufos, and 2.2 mol mg prot^-1 h^-1 forazinphos-methyl. The products from these reactions andfrom the transformation of trichlorfon and malathion,were identified by mass-spectrometry. These results,supported by specific inhibition experiments and thestringent requirement for NADPH during the in vitroassays suggest the involvement of a cytochrome P450.     

Adenosine is crucial for deep brain stimulation-mediated attenuation of tremor

Deep brain stimulation (DBS) is a widely used neurosurgical approach to treating tremor and other movement disorders. In addition, the use of DBS in a number of psychiatric diseases, including obsessive-compulsive disorders and depression, is currently being tested. Despite the rapid increase in the number of individuals with surgically implanted stimulation electrodes, the cellular pathways involved in mediating the effects of DBS remain unknown. Here we show that DBS is associated with a marked increase in the release of ATP, resulting in accumulation of its catabolic product, adenosine. Adenosine A1 receptor activation depresses excitatory transmission in the thalamus and reduces both tremor- and DBS-induced side effects. Intrathalamic infusion of A1 receptor agonists directly reduces tremor, whereas adenosine A1 receptor-null mice show involuntary movements and seizure at stimulation intensities below the therapeutic level. Furthermore, our data indicate that endogenous adenosine mechanisms are active in tremor, thus supporting the clinical notion that caffeine, a nonselective adenosine receptor antagonist, can trigger or exacerbate essential tremor. Our findings suggest that nonsynaptic mechanisms involving the activation of A1 receptors suppress tremor activity and limit stimulation-induced side effects, thereby providing a new pharmacological target to replace or improve the efficacy of DBS.     

Bird community shifts related to different forest restoration efforts: A case study from a managed habitat matrix in Mexico

Although increased attention is being paid to animals when studying restoration processes, little is known on the effects that different restoration efforts have on birds. In this study we evaluated the variation of bird communities in a managed landscape that includes cropfields and two different restoration strategies. To evaluate possible differential effects of both restoration strategies (plus former-state and natural-state comparisons as controls), we compared their bird communities. After five growing seasons, bird species richness was highest in native forest remnants and lowest in cropfields. Although species richness values from the restoration treatment did not show differences in relation to those from the forest treatment, values for the reforestation treatment did. Bird densities were highest in the forests and alike in cropfield, reforestation, and restoration treatments. However, bird communities recorded in the restoration treatment were fairly even when compared to the reforestation treatment, and highest bird species composition similarity was recorded between the restoration and forest treatments. These results suggest that the studied restoration treatment attracts a higher number of bird species in relation to former states and thus enhance bird richness. Also, we demonstrate that restoration efforts that include more actions can affect more ecosystem components. In this study, nurse plants not only offered a quick growing structural vegetation component that enhanced habitat structure, but also provided abundant food resources for birds. Given the scarcity of comparable habitat matrices to replicate our study, our results should be taken with caution as they are not generalizable to all Mexican temperate forest conditions. Although further studies need to address whether restoration practices using Lupinus elegans positively affect bird primary population parameters (e.g., survival, reproduction), our results show that restoration practices that include nurse plants can promote rich bird communities after only 5 years from the implementation of restoration measures.     

Insulin modulates PC-1 processing and recruitment in cultured human cells

We evaluated whether insulin signaling modulates plasma cell glycoprotein (PC-1) plasma membrane recruitment, posttranslational processing, and gene expression in human cultured cell lines. Insulin induced a fourfold increase (P < 0.01) of membrane PC-1 expression by rapid and sensitive mechanism(s). This effect was reduced (P < 0.05-0.01) by inhibition of phosphatidylinositol 3-kinase (200 nmol/l wortmannin) and S6 kinase (50 nmol/l rapamycin) activities and intracellular trafficking (50 micromol/l monensin) and was not accompanied by PC-1 gene expression changes. Moreover, at Western blot, insulin elicited the appearance, in both plasma membrane and cytosol, of a PC-1-related 146-kDa band (in addition to bands of 163, 117, 106, and 97 kDa observed also in absence of insulin) that was sensitive to endoglycosidase H. Finally, inhibition of PC-1 translocation to plasma membrane, by wortmannin pretreatment, increases insulin-stimulated receptor autophosphorylation. Our data indicate that insulin stimulates PC-1 posttranslational processing and translocation to the plasma membrane, which in turn impairs insulin receptor signaling. Bidirectional cross talk between insulin and PC-1, therefore, takes place, which may be part of the hormone self-desensitization mechanism.     

Local Knowledge and Economical Significance of Commercialized Wild Edible Mushrooms in the Markets of Uruapan,Michoacan, Mexico

Economic Botany - Local Knowledge and Economical Significance of Commercialized Wild Edible Mushrooms in the Markets of Uruapan, Michoacan, Mexico. Wild edible mushrooms are a non-timber forest...     

Fungal entomopathogens: new insights on their ecology

An important mechanism for insect pest control should be the use of fungal entomopathogens. Even though these organisms have been studied for more than 100 y, their effective use in the field remains elusive. Recently, however, it has been discovered that many of these entomopathogenic fungi play additional roles in nature. They are endophytes, antagonists of plant pathogens, associates with the rhizosphere, and possibly even plant growth promoting agents. These findings indicate that the ecological role of these fungi in the environment is not fully understood and limits our ability to employ them successfully for pest management. In this paper, we review the recently discovered roles played by many entomopathogenic fungi and propose new research strategies focused on alternate uses for these fungi. It seems likely that these agents can be used in multiple roles in protecting plants from pests and diseases and at the same time promoting plant growth.