Behavioural and neurochemical responses evoked by repeated exposure to an elevated open platform.

Increased psychophysiological resistance to chronic stress has been related to increased 5-HT release in the dorsal hippocampus. This study investigated the changes in 5-HT release and turnover in the hippocampus evoked by acute and repeated exposure to an inescapable stressor, an elevated open platform, and compared them to the changes evoked in the frontal cortex. Repeated exposure to this stressor results in habituation of the plasma corticosterone response to the test, with full habituation being observed after 20 trials. Repeated exposure to the stressor for 5 or 10 occasions increased 5-HT turnover in the hippocampus. By contrast, 5-HT turnover in frontal cortex was increased by acute exposure to the stressor. Microdialysis studies showed that acute stress increased 5-HT overflow in prefrontal cortex but not dorsal hippocampus whereas repeated daily (10 days) exposure to the stressor increased basal extracellular 5-HT in the dorsal hippocampus, but not the prefrontal cortex. Prior exposure to the stressor on up to 10 occasions enhanced the plasma corticosterone response to a challenge in an elevated plus-maze performed 24h later whereas repeated, but not acute, exposure to the stressor, elicited anxiolytic-like behavioural responses in this test. It is concluded that acute exposure to this form of inescapable stress selectively stimulates the 5-HT projections to the frontal cortex; repeated stress elicits a sustained increase in 5-HT release and turnover in the hippocampus. The data are consistent with the hypothesis that increased 5-HT release in the hippocampus may be implicated in the mechanisms underlying habituation to inescapable stress.

Approximate p-values for local sequence alignments: numerical studies.

Siegmund and Yakir (2000) have given an approximate p-value when two independent, identically distributed sequences from a finite alphabet are optimally aligned based on a scoring system that rewards similarities according to a general scoring matrix and penalizes gaps (insertions and deletions). The approximation involves an infinite sequence of difficult-to-compute parameters. In this paper, it is shown by numerical studies that these reduce to essentially two numerically distinct parameters, which can be computed as one-dimensional numerical integrals. For an arbitrary scoring matrix and affine gap penalty, this modified approximation is easily evaluated. Comparison with published numerical results show that it is reasonably accurate.

Mythology, narrative, and discourse in Javanese wayang: towards cross-level theories for the new development paradigm.

PIP: The field of development communication has been experiencing a paradigm shift toward an emphasis upon pluralistic, localized, and more participatory communication within the larger political and cultural environments. The emerging paradigm implicitly rejects both the ahistorical and individual-level biases of modernization theory as well as the reductionist social structural biases of dependency theory, and instead focuses upon human action within sociocultural, political, and economic contexts. There has been, however, little academic movement in the form of new theoretical formulations suited to this shift toward a new paradigm of development. This paper discusses the need for and the difficulties of cross-level theorizing in development communication which can help explain the actions of individuals within their larger sociocultural and political contexts; proposes a cross-level approach to communication and development based upon theories of mythology, discourse, and narrative; and illustrates the approach with an examination of indigenous media and the social roles of the shadow puppet (wayang) mythology in Central Java, Indonesia. Implications for applied work in development are discussed.^ieng

Anastomotic tensile strength following in situ replacement of an infected abdominal aortic graft.

The tensile strength and histologic features of anastomotic bonding were studied prior to and following in situ replacement of aortic vascular prostheses infected by Staphylococcus epidermidis. Sterile (n = 6) and infected (n = 19) Dacron grafts were used to replace the abdominal aorta of 25 dogs. After five weeks, grafts were explanted, and peak tensile force (measured in kilograms) required for anastomotic disruption was measured using a linear gain tensiometer. Anastomotic tensile strength (mean +/- SEM) of infected grafts (5.4 +/- 0.5 kg) was decreased when compared with that of sterile, control grafts (9.0 +/- 0.9 kg). The decreased anastomotic tensile strength of infected grafts was the result of an inflammatory aortitis adjacent to the suture line. Only grafts infected with the study strain of bacteria demonstrated signs of infection. In 19 dogs, the graft infection was treated by graft excision, antibiotic administration, and in situ graft replacement (Dacron or polytetrafluoroethylene prostheses). After five weeks and 12 weeks, anastomotic tensile strength of polytetrafluoroethylene (10.6 +/- 0.6 kg) and Dacron (10.8 +/- 0.5 kg) replacement grafts was similar to that of uninfected control grafts. In situ replacement of vascular prostheses infected by S epidermidis can result in graft healing with normal anastomotic bonding.

Influence of vein-patch angioplasty on carotid endarterectomy healing.

We studied the influence of venous patching on the patency, endothelial regeneration, and wall healing of endarterectomized carotid arteries in a canine model. Thirteen dogs underwent bilateral common carotid endarterectomies (intimectomy and partial media excision). In each dog, one artery was closed by continuous suture and the contralateral artery was closed by external jugular vein-patch angioplasty; arteries were excised at two postoperative intervals (two to three and four to five weeks) for light, scanning, and transmission electron microscopy. The patency of arteries closed primarily (9/13 [69%]) was not significantly different compared with arteries closed with venous patches (12/13 [92%]). By scanning electron microscopy, regeneration of the endothelial monolayer occurred by migration from the endarterectomy end points and suture lines. Despite survival of the vein-patch endothelium, the rate and pattern of reendothelialization was not altered by venous patching. In both patched and unpatched vessels, endothelial regeneration was incomplete at two to three weeks and completed by four to five weeks. The histologic characteristics of the endarterectomized arterial wall after operation were also not influenced by the closure technique. In contrast with the healing artery wall, vein-patch walls did not develop a thickened intima. Although venous patching does not influence early patency, endothelial regeneration, or wall healing after endarterectomy, vein-patch angioplasty does increase vessel diameter and prevents the development of circumferential intimal thickening, attributes that are beneficial in minimizing restenosis.