Requirement of p38 stress-activated MAP kinase for cell death in the developing retina depends on the stage of cell differentiation

The p38 members of the mitogen-activated protein kinase (MAPK) superfamily are activated by both environmental stress and endogenous signals, and may have either permissive or inhibitory roles upon both cell proliferation and cell death in the retina. We have previously shown that anisomycin, a protein synthesis inhibitor, and 2-aminopurine, a specific inhibitor of the double stranded-RNA dependent protein kinase, block apoptosis of ganglion cells induced by axotomy, and induce apoptosis of cells in the neuroblastic layer in developing rat retina. Using a specific inhibitor, we found that p38-stress activated MAP kinase is required for the death of post-mitotic cells induced by anisomycin, but not for the death of proliferating cells induced by 2-aminopurine, nor of axon-damaged retinal ganglion cells. We also show that p38 activation occurs either upstream of or parallel to the requirement for cyclic AMP to block apoptosis of post-mitotic cells, since the cyclic AMP-producing agent forskolin did not prevent p38 phosphorylation induced by anisomycin. Finally, the lack of immunostaining for phospho-p38 in apoptotic profiles suggests that p38 activation does not kill retinal cells directly, but more likely through the mediation of neighboring cells.     

Enhanced isoproterenol-induced cardiac hypertrophy in transgenic rats with low brain angiotensinogen

We have previously shown that a permanent deficiency in the brain renin-angiotensin system (RAS) may increase the sensitivity of the baroreflex control of heart rate. In this study we aimed at studying the involvement of the brain RAS in the cardiac reactivity to the beta-adrenoceptor (beta-AR) agonist isoproterenol (Iso). Transgenic rats with low brain angiotensinogen (TGR) were used. In isolated hearts, Iso induced a significantly greater increase in left ventricular (LV) pressure and maximal contraction (+dP/dt(max)) in the TGR than in the Sprague-Dawley (SD) rats. LV hypertrophy induced by Iso treatment was significantly higher in TGR than in SD rats (in g LV wt/100 g body wt, 0.28 +/- 0.004 vs. 0.24 +/- 0.004, respectively). The greater LV hypertrophy in TGR rats was associated with more pronounced downregulation of beta-AR and upregulation of LV beta-AR kinase-1 mRNA levels compared with those in SD rats. The decrease in the heart rate (HR) induced by the beta-AR antagonist metoprolol in conscious rats was significantly attenuated in TGR compared with SD rats (-9.9 +/- 1.7% vs. -18.1 +/- 1.5%), whereas the effect of parasympathetic blockade by atropine on HR was similar in both strains. These results indicate that TGR are more sensitive to beta-AR agonist-induced cardiac inotropic response and hypertrophy, possibly due to chronically low sympathetic outflow directed to the heart.     

In vivo Effects of the Anatoxin-a on Striatal Dopamine Release

Anatoxin-a is an important neurotoxin that acts a potent nicotinic acetylcholine receptor agonist. This characteristic makes anatoxin-a an important tool for the study of nicotinic receptors. Anatoxin-a has been used extensively in vitro experiments, however anatoxin-a has never been studied by in vivo microdialysis studies. This study test the effect of anatoxin-a on striatal in vivo dopamine release by microdialysis.The results of this work show that anatoxin-a evoked dopamine release in a concentration-dependent way. Atropine had not any effect on dopamine release evoked by 3.5 mM anatoxin-a. However, perfusion of nicotinic antagonists mecamylamine and α-bungarotoxin induced a total inhibition of the striatal dopamine release. Perfusion of α7*-receptors antagonists, metillycaconitine or α-bungarotoxin, partially inhibits the release of dopamine stimulated by anatoxin-a. These results show that anatoxin-a can be used as an important nicotinic agonist in the study of nicotinic receptor by in vivo microdialysis technique and also support further in vivo evidences that α7*nicotinic AChRs are implicated in the regulation of striatal dopamine release.     

Overview of the structure of all-AT oligonucleotides: organization in helices and packing interactions

We present the crystalline organization of 33 all-AT deoxyoligonucleotide duplexes, studied by x-ray diffraction. Most of them have very similar structures, with Watson-Crick basepairs and a standard average twist close to 36 degrees. The molecules are organized as parallel columns of stacked duplexes in a helical arrangement. Such organization of duplexes is very regular and repetitive: all sequences show the same pattern. It is mainly determined by the stacking of the terminal basepairs, so that the twist in the virtual TA base step between neighbor duplexes is always negative, approximately -22 degrees. The distance between the axes of parallel columns is practically identical in all cases, approximately 26 A. Interestingly, it coincides with that found in DNA viruses and fibers in their hexagonal phase. It appears to be a characteristic distance for ordered parallel DNA molecules. This feature is due to the absence of short range intermolecular forces, which are usually due to the presence of CG basepairs at the end of the oligonucleotide sequence. The duplexes apparently interact only through their diffuse ionic atmospheres. The results obtained can thus be considered as intermediate between liquid crystals, fibers, and standard crystal structures. They provide new information on medium range DNA-DNA interactions.     

Stability of Brevipalpus phoenicis (Geijskes) (Acari: Tenuipalpidae) resistance to hexythiazox in citrus groves

The false spider mite, Brevipalpus phoenicis (Geijskes), is one the most important pests of the citrus groves and transmits the citrus leprosis virus. The acaricide hexythiazox has been widely used for controlling B. phoenicis in citrus groves. The resistance of this species to hexythiazox has already been detected at high frequencies at some locations. In order to implement a resistance management program, studies were undertaken to understand the stability of the resistance of B. phoenicis to hexythiazox by 1) comparing the life-history of susceptible (S) and resistant (R) strains under laboratory conditions, and 2) evaluating the dynamics of hexythiazox resistance in citrus field plots with low (< 20%) and high (> 60%) frequency of resistance, during two years. The frequencies of resistance were estimated with direct contact bioassays on eggs with discriminating concentration of 18 mg of hexythiazox/L of water. There were no significant differences between S and R strains, based on biological parameters evaluated to build fertility life tables. However, the resistance of B. phoenicis to hexythiazox was unstable under field conditions; that is, significant reductions in the frequency of resistance were observed in the absence of selection pressure, either in citrus field plots with low or high frequency of resistance. Therefore, the instability of B. phoenicis resistance to hexythiazox can be exploited in resistance management programs.     

Induction of systemic and mucosal immune response and decrease in Streptococcus pneumoniae colonization by nasal inoculation of mice with recombinant lactic acid bacteria expressing pneumococcal surface antigen A

Mucosal epithelia constitute the first barriers to be overcome by pathogens during infection. The induction of protective IgA in this location is important for the prevention of infection and can be achieved through different mucosal immunization strategies. Lactic acid bacteria have been tested in the last few years as live vectors for the delivery of antigens at mucosal sites, with promising results. In this work, Streptococcus pneumoniae PsaA antigen was expressed in different species of lactic acid bacteria, such as Lactococcus lactis, Lactobacillus casei, Lactobacillus plantarum, and Lactobacillus helveticus. After nasal inoculation of C57Bl/6 mice, their ability to induce both systemic (IgG in serum) and mucosal (IgA in saliva, nasal and bronchial washes) anti-PsaA antibodies was determined. Immunization with L. lactis MG1363 induced very low levels of IgA and IgG, possibly by the low amount of PsaA expressed in this strain and its short persistence in the nasal mucosa. All three lactobacilli persisted in the nasal mucosa for 3 days and produced a similar amount of PsaA protein (150-250 ng per 10(9) CFU). However, L. plantarum NCDO1193 and L. helveticus ATCC15009 elicited the highest antibody response (IgA and IgG). Vaccination with recombinant lactobacilli but not with recombinant L. lactis led to a decrease in S. pneumoniae recovery from nasal mucosa upon a colonization challenge. Our results confirm that certain Lactobacillus strains have intrinsic properties that make them suitable candidates for mucosal vaccination experiments.     

Hantavirus cardiopulmonary syndrome: immune response and pathogenesis

Hantaviruses are emerging viruses in the Americas that cause cardiopulmonary syndrome with high lethality. The intense cellular immune response to hantavirus alters normal endothelial cell barrier functions and seems to be harmful to the host. On the other hand, the humoral immune response seems to be essential for recovery from infection.     

DGAT1 K232A polymorphism in Brazilian cattle breeds

Recent reports identified DGAT1 (EC 2.3.1.20) harboring a lysine to alanine substitution (K232A) as a candidate gene with a strong effect on milk production traits. Our objective was to estimate the frequency of the DGAT1 K232A polymorphism in the main Zebu and Taurine breeds in Brazil as well as in Zebu x Taurine crossbreds as a potential QTL for marker-assisted selection. Samples of 331 animals from the main Brazilian breeds, Nellore, Guzerat, Red Sindhi, Gyr, Holstein, and Gyr x Holstein F1 were genotyped for DGAT1 K232A polymorphism (A and K alleles) using the PCR-RFLP technique. The highest frequency of the A allele was found in the Holstein sample (73%) followed by Gyr x Holstein F1 (39%). Gyr and Red Sindhi showed low frequencies of A alleles (4 and 2.5%, respectively). The A allele was not found in the Nellore and Guzerat samples. Our results could be used to guide association studies between this locus and milk traits in these breeds.     

A unique vertebrate histone H1-related protamine-like protein results in an unusual sperm chromatin organization

Protamine-like proteins constitute a group of sperm nuclear basic proteins that have been shown to be related to somatic linker histones (histone H1 family). Like protamines, they usually replace the chromatin somatic histone complement during spermiogenesis; hence their name. Several of these proteins have been characterized to date in invertebrate organisms, but information about their occurrence and characterization in vertebrates is still lacking. In this sense, the genus Mullus is unique, as it is the only known vertebrate that has its sperm chromatin organized by virtually only protamine-like proteins. We show that the sperm chromatin of this organism is organized by two type I protamine-like proteins (PL-I), and we characterize the major protamine-like component of the fish Mullus surmuletus (striped red mullet). The native chromatin structure resulting from the association of these proteins with DNA was studied by micrococcal nuclease digestion as well as electron microscopy and X-ray diffraction. It is shown that the PL-I proteins organize chromatin in parallel DNA bundles of different thickness in a quite distinct arrangement that is reminiscent of the chromatin organization of those organisms that contain protamines (but not histones) in their sperm.