The effects of estradiol on avoidance learning in ovariectomized adult rats.

The present study examined the effects of ovariectomy and subsequent estradiol replacement on learning in young adult rats using a set of instrumental avoidance paradigms differing in the nature and extent of prior experience in the learning context. Thus, one group of animals was placed directly into avoidance learning (AV). A second group was trained on an appetitive task first, and then transferred into the aversive context (AP-AV). The third group was exposed to the training context without any specific appetitive response requirement, and then required to learn an active avoidance response (Context-AV). We found that estradiol (OVX+E) impaired avoidance acquisition in all cases relative ovariectomized controls (OVX). In contrast, while avoidance learning is improved following appetitive training or context exposure in both OVX+E and OVX animals, the OVX+E animals profit to a greater extent from the appetitive or context experience than do the OVX controls. We suggest that this difference may be due to enhanced attentional processes or improved hippocampal processing of contextual factors. Thus, estradiol negatively influences simple associative avoidance learning in ovariectomized rats, but appears to promote positive transfer.

Variation in distribution of the three flavivirus-specified glycoproteins detected by immunofluorescence in infected Vero cells.

Indirect immunofluorescence with rabbit antisera was used to probe the intracellular locations of the antigens of envelope, prM (precursor to structural protein M) and the nonstructural glycoproteins NS 1 (formerly described as NV 3 or SCF) specified by the flaviviruses dengue-2 and Kunjin. Perinuclear staining in various types of foci was prominent for all antigens, and the distribution was influenced by whether cells were fixed with acetone or formaldehyde. Staining of Golgi-like masses or inclusions by anti-envelope sera occurred regularly and prominently in cells infected and stained with homologous anti-envelope antibodies; in the cross reactions, such staining was largely absent, especially in dengue-2 infected cells in which it was replaced by many small circular foci scattered throughout the cytoplasm. Anti-NS 1 also stained large perinuclear inclusions and small cytoplasmic foci, but the distribution of these was dissimilar to that observed with anti-envelope sera. Anti-prM appeared to contain a mixture of antibodies of different specificities, evident at different dilutions, possibly because of different cytoplasmic locations of prM and its cleavage products. All antisera produced small discontinuous foci on the plasma membrane of unfixed infected cells; antigens of NS 1 were sometimes prominent on the surface of acetone-fixed cells.

Biochemical responses during recovery from maximal and submaximal swimming exercise.

We set out to demonstrate whether changes in plasma volume, haematocrit and some important blood constituents occurred after swimming 100 m and 800 m, as well as monitoring the duration of these changes. We measured exercise-induced changes in concentration of plasma constituents in eight subjects, and determined the expected effects of haemoconcentration on these constituents. We also investigated the different biochemical responses occurring after maximal exercise (100 m), as compared to submaximal exercise (800 m). The haematocrit increased significantly after the 100 m swim and to a lesser extent after the 800-m swim, returning to basal levels within 30 min. The plasma volume decreased by 16% on completion of the 100 m and by 8% on completion of the 800 m. The blood lactate concentration increased 15-fold and 10-fold after the 100-m and 800-m swims respectively. The plasma potassium concentration increased significantly immediately on completion of the 100-m swim, then decreased significantly at 2 1/2 and 5 min post-exercise, returning to near-basal values at 30 min. The potassium concentration measured after the 800-m event did not differ significantly from basal levels, however the measured concentrations were significantly lower than the concentrations expected on the basis of haemoconcentration. The plasma sodium concentrations measured after both 100-m and 800-m swims were significantly increased. However, calculations correcting for haemoconcentration showed significant losses in total circulating sodium.

Clinical utility of pericardial fluid pH determination.

The pH of pericardial fluid has not been well characterized. Therefore, it was analyzed in 13 consecutive patients who had pericardial disease of varying causes and were undergoing pericardiocentesis. Values ranged from 6.82 to 7.59. In seven patients with bloody pericardial effusions, the pH was significantly lower than the simultaneously determined arterial pH (7.31 +/- 0.07 versus 7.45 +/- 0.04, p less than 0.01). Pericardial fluid pH discriminated between inflammatory (pH 7.06 +/- 0.07) and noninflammatory (pH 7.42 +/- 0.06) causes (p less than 0.001). Thus, pericardial fluid pH determination is a quick and accurate method to exclude inadvertent ventricular punctures in bloody pericardiocentesis and to distinguish between inflammatory and noninflammatory causes of pericardial fluid accumulation.

Ultrastructural evidence of transport of secretory IgA across bronchial epithelium.

To define the mechanisms for transport of secretory IgA (sIgA) into bronchial secretions, IgA and secretory component in human bronchial mucosa were localized by immunoelectron microscopy. IgA was identified in plasma cells located near glandular epithelial cells and on the basolateral plasmalemma and endocytic vesicles of the epithelial cells, especially of mucous cells. Secretory component was localized to the perinuclear spaces, endoplasmic reticulum, Golgi complexes, basolateral plasmalemma and endocytic vesicles of glandular epithelial cells, as well as those of ciliated epithelial cells. These findings are consistent with a model for IgA transport in which IgA dimers, synthesized in plasma cells, are complexes with secretory component on the basolateral plasmalemma of epithelial cells in bronchial glands and transported across the cells in endocytic vesicles to the gland lumina.