Serologic survey for Toxoplasma gondii in grizzly bears from Alaska

Aquaporin-4 is a mammalian water channel protein that is predominately expressed in brain, where it is believed to mediate water homeostasis. Here we report the isolation and characterization of the cDNA for mouse Aqp4 and map the gene to the proximal region of mouse chromosome 18. This region contains the neurological mutation ataxia, but further analysis reveals that Aqp4 is not responsible for the ataxia phenotype.     

Backup compass mechanisms in pigeon orientation with the sun in the zenith

The sun is known to guide homing pigeons as a priority cue. The literature indicates that under total overcast conditions pigeons rely on a backup mechanism akin to the magnetic inclination compass for which there is much laboratory evidence in migratory birds. Total overcast conditions are not favorable for orientation research in the State of S?o Paulo, Brazil. The orientation of homing pigeons raised near the tropic of Capricorn was therefore observed around the time of the December solstice, when the sun culminated directly overhead, with a consequent interruption of the sun compass for a short time every day. In these experiments, carried out between 1981 and 1993, local geomagnetic field inclination was -25 degrees to -29 degrees 30', so that a functioning magnetic inclination compass should have been available to the birds. Whereas the birds released with sun to zenith angles between 10 degrees and 30 degrees were well oriented, both in the morning (99 vanishing bearings) and in the afternoon (143 vanishing bearings), those released with the sun less than 5 degrees away from the zenith showed random orientation (105 vanishing bearings), with no evidence of an alternative magnetic compass mechanism.     

Medical-surgical nursing: a new teaching approach and its evaluation by the student

This issue is about a teaching methodology developed by the Medical-Surgical subject of Nursing on Graduate Course at Universidade Estadual de Londrina. The teachers used the student-centered teaching process based on interpersonal relationship and problem solving method. The aim was to evaluate the last period of nursing students perception about developing of cognitive, affective and psychomotor abilities when compared with others subjects of nursing course since 1985 until 1990. This method of teaching supplied more integration among theory and practice, more ability in developing library search and oral exposition, besides more active student participation on his apprenticeship process.     

Inhibition of the hammerhead ribozyme cleavage reaction by site-specific binding of Tb

Terbium(III) [Tb(III)] was shown to inhibit the hammerhead ribozyme by competing with a single magnesium(II) ion. X-ray crystallography revealed that the Tb(III) ion binds to a site adjacent to an essential guanosine in the catalytic core of the ribozyme, approximately 10 angstroms from the cleavage site. Synthetic modifications near this binding site yielded an RNA substrate that was resistant to Tb(III) binding and capable of being cleaved, even in the presence of up to 20 micromolar Tb(III). It is suggested that the magnesium(II) ion thought to bind at this site may act as a switch, affecting the conformational changes required to achieve the transition state.     

Scintigraphic evaluation of experimental colitis in rabbits

Scintigraphic techniques are frequently used for evaluation of inflammatory bowel disease. The radiopharmaceutical of choice is labeled leukocytes. In this study, two new agents, 111In-labeled polyethylene glycol-coated liposomes and 111In-labeled human nonspecific gamma globulin (immunoglobulin G; IgG), were compared with 111In-leukocytes in a rabbit model of colitis. METHODS: In rabbits, acute colitis was induced by colonic instillation of trinitrobenzene sulfonic acid at 25 cm from the anal sphincter. After 24 hr, 15 MBq of the radiopharmaceuticals was injected intravenously in groups of four rabbits. Twenty-four hours after injection, the animals were killed and macroscopic abnormalities were scored in seven consecutive affected colonic segments of 5 cm each (0 = normal, 1 = inflammation, 2 = ulcers). The ex vivo uptake was measured in the normal ascending colon and the affected colonic segments. The colitis index (CI, affected-to-normal colon-uptake ratio) was calculated. RESULTS: Histologically, an acute, patchy, transmural colitis was observed at the site of instillation and the distal colon. The CI of all agents in colitis lesions correlated with the severity of the abnormalities. With increasing severity, the CI for liposomes was 1.86 +/- 0.24, 4.88 +/- 0.42 and 7.42 +/- 0.54 (r2 = 0.68, p < 0.001); for leukocytes 1.77 +/- 0.32, 3.10 +/- 0.58 and 5.54 +/- 0.83 (r2 = 0.31, p < 0.01); for IgG 1.60 +/- 0.29, 2.81 +/- 0.21 and 2.65 +/- 0.21 (r2 = 0.29, p < 0.02). CONCLUSION: Indium-111-labeled-leukocytes, -IgG and -liposomes all show increased uptake in inflamed colonic tissue. Indium-111-liposomes showed the highest CI, which correlates best with the morphological abnormalities. Indium-111-leukocytes and 111In-liposomes are superior to 111In-IgG for this indication.     

Regulation of hippocampal 5-HT1A receptor mRNA and binding in transgenic mice with a targeted disruption of the glucocorticoid receptor

Corticosterone is known to suppress levels of 5-HTA(1A) receptor mRNA in rat hippocampus. We describe hippocampal 5-HT(1A) receptor mRNA regulation in mice that have a targeted disruption of the glucocorticoid receptor gene. 5-HT(1A) receptor mRNA levels as well as binding of [3H]8-OH-DPAT, were measured in the hippocampus of heterozygous and homozygous GR-deficient mice and in wild-type control mice. The effect of adrenalectomy in wild-type mice and heterozygous knockouts was also studied. We hypothesized that if the glucocorticoid receptor is important as a mediator of the suppressive effect of corticosterone, this would be revealed by changed (enhanced) expression of 5-HT(1A) receptor mRNA in mice with a genetically changed glucocorticoid receptor status. It was found that 5-HT(1A) receptor mRNA levels and 5-HT(1A) receptor binding were not different in GR-deficient mice. The 5-HT(1A) receptor mRNA levels were responsive to corticosterone, as adrenalectomy led to increased levels of hippocampal 5-HT(1A) receptor mRNA both in wild-type as in heterozygous knockout mice. These increases were paralleled by small but statistically significant changes in [3H]8-OH-DPAT binding. These results support a suppressive control of B over 5-HT(1A) receptor expression in the hippocampus of the mouse, which is predominantly mediated via the mineralocorticoid receptor. The data indicates that no interaction between the two corticosteroid receptors is required for this effect of corticosterone, and that mineralocorticoid receptor-mediated suppression of gene expression can take place in the complete absence of glucocorticoid receptor.