In the normal rat, activation of ET-A receptors is partly involved in the depression of outer medullary pO2 caused by injection of iopromide. However, the decrease in OMBF after iopromide injection is not mediated by ET receptors. The beneficial effects of the ET-A receptor antagonist on CM-induced changes in outer medullary pO2 seem therefore not primarily mediated on the hemodynamic level but may rather involve tubular transport mechanisms.
Recent studies of transplanted pancreatic islets have indicated incomplete revascularization. We investigated the pH, in relation to oxygen tension (Po 2), in endogenous islets and islets syngeneically transplanted to the renal subcapsular site of nondiabetic and streptozotocin-diabetic recipients. Tissue pH and Po 2 were measured using microelectrodes. In the endogenous islets, tissue pH was similar to that in arterial blood. In the transplanted islets, tissue pH was 0.11–0.15 pH units lower. No differences in islet graft pH were seen between nondiabetic and diabetic animals, and none if the islet grafts were investigated 1 day or 1 mo posttransplantation. The Po 2 in the endogenous islets was ∼35 mmHg. Transplanted islets had a markedly lower tissue Po 2 both 1 day and 1 mo after transplantation. A negative correlation between the tissue Po 2 and the hydrogen ion concentration was seen in the 1-mo-old islet transplants in diabetic animals. In conclusion, decreased Po 2 in transplanted islets is associated with a decreased tissue pH, suggesting a shift toward more anaerobic glucose metabolism after transplantation.
The objective of this study was to assess whether signal changes can be detected in the neurovascular bundle of the mandibular canal after the extraction of a third molar. We retrospectively analyzed MRI scans of 30 test subjects with healthy mandibles and 41 patients who had had a wisdom tooth extracted. Signal intensities were measured at particular sites in the neurovascular bundle, which were defined as regions of interest (ROI) in the sagittal T1-weighted images before and after intravenous administration of a paramagnetic contrast agent. On the basis of the signal intensity increases that were measured after contrast agent administration, we compared the signal increases obtained for the patients who had received surgical treatment with the results obtained for the population of test subjects with unremarkable mandibles ( t-test, P<0.05). Compared with the healthy test subjects, patients who had received surgical treatment showed significantly higher signal intensity increases at two measurement sites, i.e., the second molar and the second premolar ( P<0.05). We found no significant differences when the measurements were performed at the first molar ( P=0.06), the third molar ( P=0.47) and in the area of the ascending mandibular ramus ( P=0.79). Compared with a population of healthy test subjects, patients who had their third molars surgically removed show higher signal intensity increases in the neurovascular bundle after intravenous contrast agent administration. The underlying cause may be the higher blood flow in the arteries and veins and the perineural plexus, which may give evidence of the pathophysiological mechanism of nerve damage in the narrow canal as a result of osteotomy.
Dated sediment cores from acidified and fishless Lake Gaffeln and Lake Härsvatten, SW Sweden, were analyzed for Daphnia ephippia and Chaoborus mandibles to test whether acidification history and fish extirpations could be reconstructed in a paleo-study using these easily identifiable animal remains. According to monitoring data fish were lost in both lakes from the 1950s to the 1970s. Progressive acidification prior to monitoring was confirmed by a gradual decrease and eventual loss of Daphnia ephippia in both study lakes during the first half of the twentieth century. In Lake Gaffeln mandibles of C. obscuripes appeared immediately after fish loss in 1973, and the regular presence of this species confirmed the succeeding fishless state of this lake. In Lake Härsvatten sediments C. obscuripes appeared only recently, i.e. three decades after fish extirpation, showing that the absence of C. obscuripes mandibles is not a trustworthy indicator of fish presence. Hence, the appearance of C. obscuripes was not temporally related to fish loss but confirmed the present fishless condition. Known historical presence of cyprinid fish in Lake Gaffeln was confirmed by a significantly higher proportion of fragmented mandibles of C. flavicans compared to the historically cyprinid-free Lake Härsvatten. In addition, both lake profiles displayed zero-proportions of fragmented mandibles during fishless periods. We conclude that acidification history and fish extirpations can be inferred by integrated studies on subfossil Daphnia ephippia and Chaoborus mandibles. However, during extreme ultraoligotrophic conditions in acidified clear-water lakes subfossil Chaoborus mandibles may be too scarce to infer fish absence/presence.
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