Impairment of brain mitochondrial function by hydrogen peroxide.

Hydrogen peroxide, at concentrations comparable to those observed under some pathological conditions, produced a concentration-dependent inhibition of state 3 (ADP-stimulated) and uncoupled mitochondrial respiratory activity. The ADP:O ratio was also substantially reduced. In contrast, the organic peroxide, t-butylhydroperoxide at the same concentrations produced no significant changes in respiratory activity. Intramitochondrial glutathione was oxidised to a similar extent in the presence of hydrogen peroxide or t-butylhydroperoxide. Thus, changes in this endogenous antioxidant apparently did not underlie the different responses to these peroxides. The effects of hydrogen peroxide were not altered by deferoxamine indicating that the extramitochondrial generation of hydroxyl radicals was not likely to be involved. However, modifications arising from the generation of hydroxyl radicals within the mitochondria remain a likely contributor to the observed deleterious effects on respiratory function. The inhibitory effects of hydrogen peroxide were greatest when pyruvate plus malate were present as respiratory substrates. Lesser inhibition was seen with glutamate plus malate and no significant inhibitory effects were detected in the presence of succinate. The findings suggest that mitochondrial components involved in pyruvate oxidation were particularly sensitive to the hydrogen peroxide treatment. However, no significant change was seen in activity of either the pyruvate dehydrogenase complex or NADH-ubiquinone oxidoreductase (complex I) when measured directly following treatment of the mitochondria with hydrogen peroxide.

Sequential feline esophageal nutrient blood flow: perfusion measurements in vivo.

The utilization of a catheter semiconductor beta detector (CASRAD) to perform in vivo, sequential, esophageal nutrient blood flow distribution studies in cats is described. A diffusable radioisotope, Rubidium 86 (86Rb), was injected intravenously and the CASRAD placed within the esophageal lumen. The distribution of 86Rb remained stable within the feline esophagus for sufficient time to allow for counting at 1.5 cm levels in the esophagus. The accuracy limitations of the CASRAD system were assessed by comparing the in vivo, recorded distribution of 86Rb with the esophageal distribution of 86Rb as determined by a well-type scintillation counter. The distribution throughout most of the esophagus was similar by both techniques. Sequential esophageal studies performed with the CASRAD showed less variability than existed in the biological differences between cats and the methodology of obtaining and counting tissue by well-type scintillation counter (mean coefficient of variation 11.6% versus coefficient of variation 23.1%).

Properties of peripherally induced persistent hindlimb flexion in rat: involvement of N-methyl-D-aspartate receptors and capsaicin-sensitive afferents.

In the sodium pentobarbital anesthetized rat, percutaneous electrical stimulation (2 mA, 7 ms, 100 Hz, 60 min) across the upper hindlimb produces an ipsilateral hindlimb flexion that persists following spinal transection. Using this preparation, the following were found. (1) Flexion was observed in both the intact and acutely spinalized (T7) rat 10 hours to two weeks following induction, but was negligible at six weeks. (2) Pretreatment of intact rats with the non-competitive N-methyl-D-aspartate (NMDA) receptor antagonists, ketamine HCl and MK-801, reduced persistent hindlimb flexion in a dose-dependent manner. (3) Pretreatment of spinalized rats with MK-801 reduced the amount of flexion, observed at 30 min following stimulation. However at 72 hrs following stimulation, administration of MK-801 to acutely spinalized rats had no effect on flexion. (4) Capsaicin pretreatment, of either neonates or adults, reduced the amount of flexion observed at 30 min following stimulation, but only adult capsaicin pretreatment reduced flexion at 72 h. (5) At 72 h following induction, bilateral dorsal rhizotomy (T11-L6) of acutely spinalized rats had no significant effect on flexion when compared to pre-rhizotomy levels. However, the subsequent removal of the hindlimb skin produced a significant reduction in flexion, and the remaining flexion was eliminated by the removal of the thoracolumbar spinal cord and cauda equina. These combined results suggest that prolonged activation of C-afferents and NMDA receptors induce a persistent hindlimb flexion in rat that is maintained at the level of the spinal cord.

Inhibition of chronic hindlimb flexion in rat: evidence for mediation by 5-hydroxytryptamine.

Prolonged high-intensity stimulation of the rat hindlimb produces a persistent unilateral flexion. 5-Hydroxytryptamine (5-HT) has been implicated in the modulation of spinal cord mechanisms. Electrical stimulation across the upper hindlimb was used to induce a persistent hindlimb flexion. The flexion was measured after stimulation and at 72 h, both before and after spinal transection at T7. Transection of the spinal cord typically resulted in an increase in flexion of 3-5 g (rebound). Pretreatment with para-chlorophenylalanine (pCPA) to deplete 5-HT, or the administration of metergoline, a non-specific 5-HT antagonist, had no significant effect on flexion at 72 h in the intact rat but abolished rebound. The 5-HT1A agonist, (+-)-8-hydroxy-2-(di-N-propylamino)tetralin hydrobromide (8-OH-DPAT) and 5-HT1B agonist, m-trifluoromethylphenylpiperazine-HCl (TFMPP), had no effect on flexion at 72 h in the intact rat but reduced rebound. The 5-HT2 agonist, 1-(2.5-dimethoxy-4-iodophenyl)-2-aminopropane-HCl (DOI), suppressed post-stimulation flexion and flexion subsequent to spinal section. Furthermore, ketanserin, a 5-HT2 antagonist, restored flexion suppressed by DOI in the acutely spinalized rat. These results suggest that chronic hindlimb flexion is suppressed in the intact rat by descending, serotonergic fibers which exert an effect through spinal 5-HT2 receptors. Moreover, 5-HT1 agonist suppression of rebound implicates these receptors as well in the modulation of chronic hindlimb flexion.

Improved recovery of highly enriched mitochondrial fractions from small brain tissue samples.

The investigation of mitochondrial abnormalities in brain commonly requires isolation of these organelles from small tissue samples. We have modified a mitochondrial isolation procedure based on Percoll density gradient centrifugation to increase the proportion of the total mitochondrial pool recovered while reducing contamination with synaptosomes and related structures containing cytoplasm. Initially, myelin was removed by centrifugation in 12% Percoll in isotonic buffer. The pellet was resuspended, treated with digitonin to break up synaptosomes and similar structures and subjected to discontinuous Percoll density gradient centrifugation. The mitochondrial fraction obtained from this procedure was highly metabolically active and well coupled, exhibiting respiratory control ratios above 5. The recovery of mitochondrial markers using a single rat forebrain as starting material was approximately 18% to 21%. When small tissue samples (approximately 50 mg wet weight) were used as starting material the recovery of the mitochondrial marker was approximately 16%. The ratio of recovery of a mitochondrial marker to the cytoplasmic marker lactate dehydrogenase exceeded 200 in preparations from a single rat forebrain. This is substantially greater than values reported for previously published procedures reflecting both an improved yield of mitochondria and a reduction in cytoplasmic contamination.

The role of the Internet in medical decision making.

The Internet has dramatically changed the means by which information is obtained. Accurate, up-to-date information is vital to maintain the quality of healthcare, especially as US healthcare delivery changes to a primary care-based system. The availability of this new and potentially vast source of information also affects strategies for medical decision making. In this article, use of online information in our medical center is discussed, together with the impact of a locally-developed decision support system. This system first contained components for differential diagnosis as well as computer-assisted instruction. Initially, online searching was limited to Medline literature searches. This component has now been expanded to include important new tools for accessing medical information on the Internet.

Choroidal thickness in regressed retinopathy of prematurity.

PURPOSE: To compare choroidal thickness in patients with regressed retinopathy of prematurity (ROP) with healthy controls using enhanced depth imaging optical coherence tomography (EDI OCT) METHODS: Twenty-four children and young adults (41 eyes) with regressed ROP≥stage 3 had undergone EDI OCT with Spectralis FD-OCT as part of their clinical record. Their refraction, best-corrected visual acuity, and ophthalmoscopic findings were recorded. Corresponding data was collected prospectively from 33 healthy controls (58 eyes) who had been born at term. Choroidal thickness was measured independently by two observers subfoveally and at 1500 µm nasal and temporal to the fovea using EDI OCT. RESULTS: Mean subfoveal choroidal thickness, adjusted for refraction, was 271.1 µm (95% CI, 247.8-294.5) in the ex-ROP group, which was significantly thinner than 327.4 µm (95% CI, 293.8-360.9) in controls (P=0.008). Similarly, mean adjusted temporal choroidal thickness was 257.2 µm (95% CI, 240.2-274.2) in ex-ROP's vs 320.5 µm (95% CI, 288.6-352.3) in controls (P=0.001). There was no statistically significant difference in the nasal measurement. In the ex-ROP group, there was no significant correlation between subfoveal choroidal thickness and gestational age (r(s)=0.16, P=0.46) or birthweight (r(s)=0.03, P=0.90). In eyes without copathology in addition to regressed ROP (29 eyes, 19 patients), there was no significant correlation between subfoveal choroidal thickness and visual acuity. CONCLUSIONS: Our findings of thinner subfoveal and temporal macular choroidal thickness in regressed ROP support the case for choroidal involvement in the pathogenesis of this condition.

"Is this the liberry?".

The importance of a library in the hospital setting is discussed. Suggestions on how to start a library, build library holdings, develop a story hour, and promote a library are provided.

Secondary esophageal tumors.

Secondary esophageal carcinoma usually originates from a primary site in either the lung or breast and produces obstruction and symptoms that frequently mimic a benign esophageal stricture or primary esophageal carcinoma. Esophagoscopy shows a smooth identation, usually covered with normal mucosa; the appearance resembles a benign esophageal stricture. Esophageal biopsy in patients with secondary tumors is often negative for carcinoma. The radiologist plays a significant diagnostic role by his ability to show that the cause of the stricture is extramucosal and may be due to a secondary carcinoma involving the esophagus.

Endometrial stromal sarcoma of the broad ligament arising in an area of endometriosis in a paramesonephric cyst. Case report.

A 63-year-old Jamaican negress had an endometrial stromal sarcoma arising in a paramesonephric cyst of the broad ligament. Morphological evidence is presented to show that the tumour arose from an area of endometriosis within the cyst wall. Subsequent metastases responded for a few months to cyclophosphamide therapy and the patient died 14 months after the onset of symptoms.

Mitochondrial respiratory function and cell death in focal cerebral ischemia.

Pyruvate-supported oxygen uptake was determined as a measure of the functional capacity of mitochondria obtained from rat brain during unilateral middle cerebral artery occlusion and reperfusion. During ischemia, substantial reductions developed in both ADP-stimulated and uncoupled respiration in tissue from the focus of the affected area in the striatum and cortex. A similar pattern of change but with lesser reductions was seen in the adjacent perifocal tissue. Succinate-supported respiration was more affected than that with pyruvate in perifocal tissue at 2 h of ischemia, suggesting additional alterations to mitochondrial components in this tissue. Mitochondrial respiratory activity recovered fully in samples from the cortex, but not the striatum, within the first hour of reperfusion following 2 h of ischemia and remained similar to control values at 3 h of reperfusion. In contrast, impairment of the functional capacity of mitochondria from all three regions was seen in the first 3 h of reperfusion following 3 h of ischemia. Extensive infarction generally affecting the cortical focal tissue with more variable involvement of the perifocal tissue developed following 2 h of focal ischemia. Thus, mitochondrial impairment during the first 3 h of reperfusion was apparently not essential for tissue infarction to develop. Nonetheless, the observed mitochondrial changes could contribute to the damage produced by permanent focal ischemia as well as the larger infarcts produced when reperfusion was initiated following 3 h of ischemia.

Pseudotumor caused by gastric varices.

On upper-gastrointestinal examination a patient with cirrhosis of the liver was found to have prominent gastric varices presenting as a pseudotumor near the cardia. The diagnosis of varices was confirmed by gastroscopy and angiography. A correct diagnosis is necessary to avoid an ill-advised biopsy or unwarranted surgery.

Sodium channel kinetics in normal and denervated rabbit muscle membrane.

The effects of chronic denervation on sodium (Na) channels in rabbit muscle membrane were determined using intracellular microelectrodes and Vaseline gap voltage clamp techniques. The Hodgkin-Huxley model was used to describe the kinetic and steady-state parameters of channel activation and fast inactivation. Chronic (7-10 days) denervation was found to cause a decreased resting potential, lowered action potential peak, and fibrillation potentials in rabbit extensor digitorum longus (EDL) muscles. Under voltage clamp conditions, no differences were observed between denervated and normal fibers in the voltage dependence of the steady-state Na channel activation and fast inactivation curves, or in the time course of development of fast inactivation. However, in denervated fibers, the time course of recovery from fast inactivation was approximately half that measured in normal fibers. Also, whereas depolarizing holding potentials induced a long-term inactivation to varying degrees in normal EDL fibers, denervated EDL fibers and normal soleus fibers were uniformly resistant to prolonged depolarization. These results suggest that the denervation-induced development of spontaneous activity may be due in part to changes in the mechanisms that control the refractoriness of Na channels.

Double-contrast esophagrams. The prone technique.

The authors describe a simple method for obtaining double-contrast images of the lower esophagus with the patient in a prone position. This technique has a high success rate, allows repeated imaging, and is easily incorporated into routine upper gastrointestinal studies. Diagnostic double-contrast studies were obtained in 78% of 28 patients. Ten abnormalities, including a Mallory-Weiss tear, were demonstrated. Single-contrast esophagrams, performed immediately afterwards, demonstrated only six abnormalities.

Cytologic bile examination in the diagnosis of biliary duct neoplastic strictures.

Cytodiagnosis of the bile is not frequently thought of as a method of obtaining a histopathologic diagnosis of the cause of a neoplastic biliary duct stricture. However, cells surrounding the biliary ducts are continuously exfoliated into bile and become available for cytologic examination whenever bile is collected. Nineteen patients with obstructive jaundice are reported. In seven of 15 with neoplastic biliary duct strictures, cytodiagnostic examination showed tumor cells. There were no false-positive results. The sensitivity of bile cytodiagnosis in this series was 47%, its specificity was 100%, and its accuracy was 58%.

Direct calibration of a totally implantable pulsed Doppler ultrasonic blood flowmeter.

A totally implantable pulsed Doppler ultrasonic blood flowmeter has recently been developed to provide information on the velocity-flow profile in a vessel as well as its diameter. Volume flow can be indirectly obtained according to the formula: Q = (phi/4)(diam)2-v. In order to determine the accuracy of this estimate, in vivo direct bleedout measurements were performed on the abdominal aorta of six dogs with an overall accuracy in 77 trials of +2.0 +/- 8.7% (mean +/- 1 SD). The best-fit mean linear regression line was found to be: flowmeter output = 1.013-true flow + 5.1 ml/min. The scatter in the flowmeter's accuracy is thought to be due to small variations in the angle of the transducer. The source of the 2% overestimation in the mean accuracy could not be directly attributed to any one condition; the error is sufficiently small that in many cases it can be neglected.

Brain mitochondrial responses to postischemic reperfusion: a role for calcium and hydrogen peroxide?

During early recirculation following global brain ischemia, mitochondria are exposed to markedly elevated Ca(2+) concentrations and a short-lived production of reactive oxygen species, including hydrogen peroxide (H(2)O(2)). A brief increase in mitochondrial Ca(2+) and a subsequent increase in mitochondrial glutathione content have been observed. In the present study, we have confirmed the increase in mitochondrial glutathione in a rat model of global forebrain ischemia. This change was not inhibited by treatment of the rats with FK506, contrasting with our previous finding that cyclosporin A partially blocked the increase. These results suggest that induction of the mitochondrial permeability transition may be necessary for the increase in glutathione content in these organelles. To further investigate possible mitochondrial responses during early postischemic reperfusion, mitochondria isolated from normal brain were exposed to Ca(2+) and H(2)O(2), under conditions similar to those in intact cells. Respiratory activity was substantially modified when the mitochondria were exposed to Ca(2+) and H(2)O(2) together. Two distinct and largely noninteracting mechanisms apparently accounted for the responses to these agents. The effects of Ca(2+), but not H(2)O(2), were inhibited by cyclosporin A, again implicating the permeability transition in some of the mitochondrial changes.