Effects of afferent and efferent celiac nerves on acute gastric lesions: due to changes in blood flow?

Since ablation of afferent nerves prior to stress results in increased severity of acute gastric mucosal lesions, afferent nerves are thought to mediate protective mechanisms in the stomach. These mechanisms are known to include vasodilation of gastric mucosal vessels; vasodilation is thought to allow the gastric mucosa to respond to injurious substances. However, it is not known whether other aspects of mucosal health, independent of those caused by increased blood blow, are affected by afferent blockade. This study compared gastric blood flow and acute gastric mucosal lesions during stress in rats with either chemical sympathectomy or afferent blockade. The purpose of the study was to compare the lesion index and blood flow in each treatment group. The lesion index was highest in rats with afferent blockade and lowest after sympathectomy. Gastric blood flow was partially preserved after sympathectomy, but was not greatly increased, suggesting that some of the effects observed after afferent blockade are unrelated to changes in blood flow.

Inhibition of afferent vagus nerves decreases gastric stress lesions.

Capsaicin (Sigma Chemical Co.) is a unique chemical agent that causes degeneration of afferent nerve fibers. Previous conclusions about Capsaicin effects on the gastric mucosal response to stress have not precisely defined which afferent nerves were affected. Therefore, the aim of the first portion of this study was to define the origin of afferent vagus nerves to the anterior gastric wall after injections of fluorogold (which is an axonal tracer) into the stomach. The second part of this study was to compare the stress effects on the gastric mucosa in rats with impaired afferent nerve function after Capsaicin treatment.

An Internet atlas of mouse development.

A prototype two- and three-dimensional color atlas of mouse development is described. The prototype has been developed using two embryos, a 13.5 d normal mouse embryo and a PATCH mutant embryo of the same age. Serial sections of the embryos, with an external registration marker system, introduced into the paraffin embedding process, were prepared by standard histological methods. For the 2D atlas, color images were digitized from 100 consecutive sections of the normal embryo. For the 3D atlas, 300 gray scale images digitized from the mutant embryo were conformally warped and reconstructed into a 3D volume dataset. The external fiducial system facilitated the three-dimensional reconstruction by providing accurate registration of consecutive images and also allowed for precise spatial calibration and the correction for warping artifacts. The atlases, with their associated anatomical knowledge base, will be integrated into a multimedia on-line information resource via the Internet's World Wide Web (WWW) using an enhanced (patent pending, Eòlas Technologies) version of the Mosaic WWW browser program from the National Center for Supercomputer Applications. These programs will provide research biologists with a set of advanced tools to analyze normal and abnormal development.

The visible embryo project: embedded program objects for knowledge access, creation and management through the World Wide Web.

We have designed a prototype knowledge management online environment for the biomedical sciences which integrates access to online representations of the scientific literature, bibliographic databases, high-performance visualization technologies, large-scale scientific databases, and tools for authoring new-generation scientific publications. This system will provide widespread access to its resources by using the World Wide Web for its underlying architecture. This system expands upon our Weblet Interactive Remote Visualization (IRV) server technology to produce a set of dedicated Internet "visualization servers" which provide interactive control of real-time visualizations from the Visible Embryo Project database from within Web pages viewed with our WebRouser software package. This system will be used to develop a set of prototype applications for both online education of medical students in developmental anatomy and for an interactive patient education system for expectant parents. We recognize that knowledge represented by these national resource databases is not static, therefore it is essential to include tools for both the creation of new "compound documents" which incorporate embedded objects, as well as for managing the peer-review of scholarly publications, in order to ensure the integrity of new knowledge as it is added to these databases in the future. We have therefore begun to design integrated tools for our system which facilitate both the creation of and the validation of new generations of scientific knowledge.

Is there a rationale for regionalizing organ transplantation services?

This paper explores issues in the designation of centers to provide organ transplantation procedures and aftercare, a decision faced increasingly by policymakers, planners, and payers. As background for consideration of the regionalization of organ transplantation services, an array of models of regionalization of health services, ranging from full-scale vertical integration to market-enhancing information provision, is described. In the United States, regionalization has mainly followed the designation model within the certificate-of-need system; vertical integration has been adopted only in limited ways. Next, the authors' review of current approaches to the regionalization of organ transplantation centers by public and private payers indicates that designation of centers is increasing, although the empirical evidence concerning the classes of hospitals upon which designation decisions rest is weak. The authors then review the literature on the relationship between volumes and outcomes on surgical services with particular reference to organ transplantation, which on the whole suggests that a relationship between volumes and outcomes exists. Original empirical analysis of data on kidney transplants that were secured from the Health Care Financing Administration is then presented. The study of the effects of hospital and surgeon volumes on graft and patient survival and of the effect of volume on charges found no systematic influence of hospital or surgeon volumes on graft or patient survival. Some evidence that charges are lower for larger centers was found. The authors conclude that the evidence implies that using volume as the provider characteristic upon which to base designation of transplantation centers is problematic, at least for kidney transplants. Steps policymakers might take to ensure quality of transplantation services is discussed in the final section.

The ipsilateral organization of the afferent nerves to the stomach.

In previous nerve tracing studies we found evidence that the efferent gastric vagus nerves supplying the anterior gastric wall had a regional organization. The first part of this study aimed to determine whether vagus afferent nerve cells supplying the stomach have a regional organization; an ipsilateral pattern of innervation was found. Next, selective blockade of the afferent nerves was performed and verified by axonal tracing. Animals with afferent blockade were stressed to determine the effect of afferent nerve blockade on the gastric stress response. After selective blockade of afferent vagus nerves to the anterior gastric wall in rats, water-immersion stress was then applied. The part of the gastric wall with afferent nerve blockade had fewer acute gastric lesions than control animals or the contralateral side of the stomach after 24 hr of stress. This study supports the hypothesis that afferent as well as efferent vagus nerves have an ipsilateral arrangement. Afferent nerve blockade of the left vagus nerve protected the anterior wall of the stomach against stress ulceration.