Skeletal muscle capillary flow and oxygenation in hypoxic hypoxia: effect of a 5-HT2 receptor antagonist.
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Animals↗
Biomedical subjects
D H Lewis
Publications and source records attributed to D H Lewis.
Microscopic and ultrastructural studies of necrotizing hepatopancreatitis in Pacific white shrimp (Penaeus vannamei) cultured in Texas.
Granulomatous hepatopancreatitis of unknown etiology has been considered an important disease of Texas shrimp mariculture since 1985. Samples of Pacific white shrimp (Penaeus vannamei) were collected during 1986, 1987, and 1990 from three farms and an experimental mariculture facility with histories of production loss and increased mortality rates. Histologic and ultrastructural examination of shrimp from the four sites demonstrated two morphologically distinct, Gram-negative, double-enveloped, intracytoplasmic bacteria in necrotic hepatopancreatic epithelium. The more numerous small, pleomorphic rod as well as the helical organism are both taxonomically unclassifiable. The helical organism lacked ultrastructural characteristics of previously described helical or spiral bacteria. The relationship between the two organisms is unknown, but the pleomorphic rod is thought to play a major role in the disease. The role of a bacterial agent(s) in subsequent disease episodes is suggested by the observation that the use of oxytetracycline-medicated feed resulted in increased production and survival. Hepatopancreatic tubular epithelial necrosis and shrimp mortality correlated directly with the extent of infection by the small pleomorphic rod. Individual discrete bacteria were identified microscopically by Steiner and Steiner's method. Three major developmental stages of the disease were characterized based on the extent and number of hepatopancreatic tubular epithelial cells containing bacteria, the degree of tubular interstitial inflammation, and the extent and chronicity of tubular necrosis. Additional studies are needed to clarify the roles of the different bacteria identified and the potential role of environmental factors on the disease process.
Animals↗
Orthodontic/restorative interface.
There have been many advances in orthodontic and restorative procedures. These can be combined to provide a very powerful tool in providing the optimum results. This article describes when a combined approach would be appropriate and discusses how the various problems are overcome.
Anodontia↗
Brain SPECT and the effect of cerebral angioplasty in delayed ischemia due to vasospasm.
Cerebral vasospasm is a major determinant of outcome after subarachnoid hemorrhage (SAH). Brain SPECT with 99mTc-HMPAO was obtained before and after cerebral angioplasty in 10 patients with delayed ischemia due to vasospasm. Eight patients had clinically evident neurologic improvement after the procedure. Visual interpretation and an internal-reference (cerebellum), manual, semi-quantitative region of interest (ROI) analysis revealed improvement of regional cerebral blood flow (rCBF) in 9 out of 10. There were disagreements between the visual and ROI analysis in the two that did not improve clinically. For all 10, the average increase per anterior circulation vessel dilated (n = 17) was 8.8% by comparison of the corticocerebellar ratios. For the eight that improved, the average increase was 10.5%. Brain SPECT is valuable for evaluating delayed cerebral ischemia caused by vasospasm after SAH and is useful to document the changes in rCBF induced by angioplasty. It is possible that SPECT may be useful to detect critical reductions in perfusion before clinical deficits develop, thereby offering the potential to identify candidates for early treatment with angioplasty.
Adult↗
Vasomotion in rat skeletal muscle induced by hemorrhage as recorded by laser-Doppler flowmetry.
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Animals↗
Evaluation of red blood cell and plasma flow and volume by the use of a dynamic and dual static acquisition radionuclide technique in arterial flaps in sheep.
The aim of this study was to investigate whether in the distal, poorly perfused part of a flap the pressure gradient remains sufficient to allow flow of plasma and red blood cells (RBCs) within the first hour after flap elevation. For this purpose 99Tcm-labelled RBCs and 111In-chloride-labelled plasma proteins in an arterial skin flap that extended beyond the boundaries of its vascular territory in sheep has been used. Flow information was derived for both plasma and RBCs from dynamic acquisitions, while volume information was derived from dual energy static acquisition at equilibrium (steady-state). Results indicate that the mean flow and the mean volume of plasma are equal through the entire length of the flap. Although the flow is minimal, there is no stasis of plasma in the poorly perfused part of the flap. By comparing the mean flow of RBCs to their mean volume, no difference is seen in the well-perfused proximal two-thirds of the flap. In the distal, poorly perfused part, flow decreases while the volume increases. The increased volume of RBCs at minimal flow indicate pooling of RBCs in this region already in the first hour after flap elevation.
Animals↗
Extracellular muscle surface pO2 and pH heterogeneity during hypovolemia and after reperfusion.
Tissue pO2 (ptO2) and pH (ptH) in skeletal muscle are known to be affected at an early stage of hemorrhage. This study examines the effects of hypovolemia on the extracellular ptO2 and ptH distributions at multiple tissue sites using a recently developed multipoint microelectrode, that provides simultaneous measurements of ptO2 and ptH. The results show that the development of tissue acidosis occurs in spatially different patterns and that the magnitude of the acidosis at some tissue sites is larger and remains longer than previously known. The changes described are believed to be due to the heterogeneous blood flow seen during shock and after reperfusion. The degree of local acidosis was correlated to the relative decrease in oxygen tension at that particular site. These new findings can be of importance for the development of future resuscitative measures as well as in constructing patient monitoring systems.
Animals↗
Benefit of tomography in the scintigraphic localization of cerebrospinal fluid leak.
A CSF leak was demonstrated by tomography after planar acquisition failed to localize it. The rotatogram was more definitive than the reconstructed images in showing the leak. Tomography should be considered when the leak may be in an unusual location and the patient does not have rhinorrhea or otorrhea. Tomography allows a complete 360 degrees survey to examine for the best angle for inspection of the leak, whereas the empirically oriented planar study can sample only limited projections, particularly if given time limitations for acquisition.
Adult↗
Evaluation of the microcirculation in a sheep island pedicle flap with laser Doppler flowmeter and 99m-Tc-labelled red blood cells.
The aim of the study was experimentally to evaluate the capability and reliability of laser Doppler flowmetry (LDF) in conditions of circulatory deficiency, by correlating it to flow-related parameters measured by a radionuclide-imaging technique and using 99m-Tc red blood cells (RBCs). For this purpose, a pedicle island flap in the sheep was used, with well-perfused proximal parts and with evident stasis in the distal third of the flap. No correlation was found between results obtained with the two techniques. In regions with evident stasis, falsely high LDF readings were recorded. This may be due to a back-and-forth motion of the RBCs under the probe, rather than to true flow. It was concluded that, while LDF seems reliable in detecting complete arterial occlusion, it is unreliable in predicting either complete venous occlusion or partial obstruction of the flow to and from the flap. Clinical use for this purpose cannot be recommended.
Animals↗
Effect of hyperoxemia and ritanserin on skeletal muscle microflow.
Serotonin2 (5-HT2) receptor antagonists (ketanserin, ritanserin) can normalize a hyperoxemia-induced disturbance in skeletal muscle oxygenation, presumably by local microflow changes. The purpose of this study was to develop equipment for local hydrogen clearance measurements with a modified eight-channel platinum electrode to assess changes in local skeletal muscle capillary blood flow induced by hyperoxemia and ritanserin (0.035 mg/kg) during hyperoxemia. Laser-Doppler flowmetry was used for regional microflow measurements. Two groups of six anesthetized and artificially ventilated rabbits were studied: group I with normoxemia and hyperoxemia [arterial PO2 (PaO2) 48 kPa; 360 Torr] and group II before and after ritanserin with hyperoxemia (PaO2 46 kPa; 345 Torr). In group I, hyperoxemia induced a mean local hydrogen clearance decrease of 22% while laser-Doppler flowmetry signal decreased 31%. In group II, ritanserin induced a 125% mean local hydrogen clearance increase compared with hyperoxemia (or 37% compared with group I normoxemia); laser-Doppler flowmetry signal increased 30%. The sum distribution of local hydrogen clearances shifted to the left during hyperoxemia and to the right after ritanserin. The conclusion from this study is that local and regional microflow changes can explain the effects of hyperoxemia and ritanserin on skeletal muscle oxygenation.
Animals↗
The accumulation of polymorphonuclear leukocytes in post-ischemic skeletal muscle in the rat, measured by quantitating tissue myeloperoxidase.
In the present study we have evaluated the activity of myeloperoxidase (MPO) in ischemic reperfused skeletal muscle of rats, as an index of polymorphonuclear leukocyte (PMNL) accumulation and its time course. A tourniquet model for temporary ischemia was used, in which one hindleg was made ischemic for 1.5, 3 or 5 hours. Muscle biopsies were taken after 12 hours reperfusion from both the injured and the uninjured legs. Controls received anesthesia only. No increase in the MPO levels was observed after 1.5 hours of ischemia followed by 12 hours of reperfusion. With the same reperfusion time and 3 or 5 hours of ischemia, there was a five-fold increase in MPO activity. Prolonging the ischemia from 3 to 5 hours did not cause any further significant MPO increase. With 3 hours of ischemia, biopsies were also taken after 0, 1, 5, 24 and 74 hours reperfusion. The results showed a time dependent increase in MPO activity. A significant increase was first seen after 5 hours reperfusion with the peak at 24 hours. After 74 hours of reperfusion the MPO activity had almost returned to control levels. The uninjured leg had MPO levels similar to those in the control. However, there was a small reduction at 5 and 12 hours of reperfusion. During the ischemic period before reperfusion, the ischemic leg showed a significant decrease in MPO activity. Severe ischemia in skeletal muscle results in a time dependent accumulation of PMNLs during reperfusion, as measured by the changes in MPO activity in the tissue.
Animals↗
The relationship between blood flow, development of edema and leukocyte accumulation in post-ischemic rat skeletal muscle.
The relationship between blood flow (xenon washout method), edema formation (percent total water content), and the number of polymorphonuclear leukocytes (PMNLs), as measured by the level of the enzyme myeloperoxidase, has been investigated in post-ischemic skeletal muscle of rats. A tourniquet model of temporary, complete ischemia of one hindlimb for 3 or 4 hours was used. Biopsies were taken after 0.5, 5 and 12 hours of reperfusion (6 experimental groups) and from a control group that had received only anesthesia. After 4 hours, but not 3 hours of ischemia there was a restricted blood flow during the early reperfusion phase, the "no-reflow" phenomenon, indicating severe ischemia. There was no significant accumulation of PMNLs in the skeletal muscle nor was there a correlation between the number of PMNLs in the post-ischemic muscle and the restricted bloodflow. With 4 hours of ischemia and 0.5 hours of reperfusion there was a statistically significant, positive correlation between the number of PMNLs and the amount of edema; no such correlation was evident in either of the other groups. These results suggest that PMNLs are not the major cause of reduced bloodflow or of edema in the early reperfusion phase after total ischemia.
Animals↗
The relation of the post-ischemic reperfusion impairment to the severity of ischemia in the tibialis anterior muscle of the rat.
Hyperemic volume flow rates were followed during 15 minutes of post-ischemic reperfusion in tibialis anterior muscle of the rat after 1, 2 and 3 hours of tourniquet ischemia using the 133Xenon clearance technique. Results showed a no-reflow phenomenon after 2 and 3 hours of ischemia. There was a marked impairment in flow, seen immediately upon reperfusion as a reduction or abolishment of the initial peak of the normally brisk post-ischemic hyperemia. The impairment increased with increasing duration of ischemia. The range of maximal peak hyperemic flow rates was wide and median maximal peak flows were 43.1, 14.6 and 7.2 ml.min-1.100 g-1 after 1.2 and 3 hours, respectively. This reflow impairment was not caused by differences in arterial blood pressure at the start of perfusion or during the initial 2 minutes of perfusion. Venous hematocrit at the start of the reperfusion was not significantly different between the three groups. Total muscle water of 75.9% in control muscle increased to 79.7% after 3 hours of ischemia and 1 hour of reperfusion and reached a maximum of 85.7% after 5 hours of reperfusion, demonstrating that the no-reflow seen during the initial 15 minutes could not be caused by an increased tissue pressure due to rapidly developing reperfusion edema. Results indicate a microvascular hindrance in post-ischemic reperfusion.
Animals↗
The effect of hypervolemic hemodilution and hyperoncotic infusions on the immediate reperfusion impairment in skeletal muscle of the rat after prolonged total ischemia.
The effect of hypervolemic hemodilution and hyperoncotic infusions on the reactive hyperemic volume flow rates during the initial minutes of post-ischemic reperfusion in the rat's tibialis anterior muscle after 1, 2 and 3 hours of tourniquet ischemia was studied using the 133Xenon clearance technique. Median maximal hyperemic peak reflow rates in muscle of non-infused, control animals upon release of a tourniquet were 56.5, 43.6 and 7.5 ml.min-1 x 100 g-1 respectively, demonstrating the development of a post-ischemic reperfusion impairment, a no-reflow phenomenon, that increased with the duration of the preceding period of ischemia. Rapid infusions of isotonic saline solutions over the last five minutes of tourniquet ischemia, aiming at increasing the circulating blood volume of the animals at start of the ischemic leg reperfusion by 2.0, 4.5, and 9.5 ml respectively, or by approximately 10%, 25% and 50%, gave no significant improvement in post-ischemic reperfusion, except in that following 3 hours of leg ischemia and after the two largest volumes. Rapid infusions of solutions of human albumin in a concentration of 200 mg.ml-1 to an amount approximately equalling 0.15, 0.40 and 0.75 g.kg-1 bodyweight till the moment the reperfusion was started, aiming to increase circulating albumin until the start of reperfusion by about 10%, 20% and 40%, significantly improved immediate peak hyperemic reperfusion in proportion to dose and more than doubled post-ischemic peak hyperemic reperfusion rates after the largest dose to 129.6, 102.6 and 39.1 ml.min-1 x 100 g-1 respectively. This improvement in initial post-ischemic hyperemia by hyperoncotic reperfusion may be of importance for achieving a rapid post-ischemic tissue oxygenation and for preventing tissue edema.
Albumins↗
An approach to the treatment of malocclusion caused by bone expanding lesions.
A case is described in which fixed orthodontic appliances were used to correct a malocclusion complicated by the local effects of a dentigerous cyst.
Child↗
Radionuclide methodology for the assessment of the microcirculation in island pedicle flaps in a sheep model.
Island pedicle flaps with a proximal well-perfused part and a distal poorly-perfused part were raised in eight anaesthetized sheep. Autologous red blood cells were labelled in vitro with 99TcmO4 and plasma with 111In chloride. The labelled cells and plasma were injected intraarterially and both dynamic and static images of the time-course of radioactivity were obtained with a gamma camera. Time activity curves were generated for selected regions of interest of the flap. For both plasma and red cells there was a substantial decline in the amount of tracer reaching the distal part of the flap; the time to maximum counts increased and the time activity curves indicated a minor uptake and almost no clearance pattern. In general there were marked local differences in the flow of plasma and red cells. The flow of plasma was more rapid than that of the red cells in five of the eight sheep. The model provides a standardized pedicle flap having a proximal part with adequate circulation and a distal part with inadequate circulation. It is concluded that this sheep model is suitable for radionuclide studies examining those factors that influence the distribution of blood flow within this tissue.
Animals↗
Lipid peroxidation products in postischemic skeletal muscle and after treatment with hyperbaric oxygen.
Earlier studies from our laboratory have shown that hyperbaric oxygen (HBO) treatment reduces edema, enhances aerobic metabolism and improves the recovery of the phosphorylase activity in postischemic rat skeletal muscle. However, as it has become increasingly apparent that oxygen in excess may have harmful effects, it was of interest to study if HBO caused an increased formation of oxygen free radicals. Toxic peroxides, as a result of oxygen free radicals, were quantitated in the postischemic skeletal muscle of rat and with HBO treatment by measuring the thiobarbituric acid reaction which includes the lipid peroxides and the alkydes including malondialdehyde (MDA), a key intermediate in the formation of peroxides. A tourniquet model of temporary ischemia of the rat hindlimb was used for 3 hours. Muscle biopsies were taken at various intervals before and after tourniquet release with and without hyperbaric oxygen at 2.5 atmospheres absolute (ATA) for 45 min after tourniquet release. Three hours of anesthesia caused a significant rise of thiobarbituric acid reactive material (TBAR) concentration in muscle compared to normal controls without anesthesia. An increase of similar magnitude was seen after 3 hours of ischemia, with or without reperfusion. These values were normalized after 45 min. HBO in the postischemic phase did not cause a further increase in the TBAR concentration in muscle immediately postischemically. However, the levels remained increased at 45 min after the onset of reperfusion, immediately after HBO treatment and had returned to normal values 2 hours postischemically.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
The surgical correction of mandibular prognathism using rigid internal fixation--a report of a new technique together with long-term stability.
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Diagnosis, Differential↗