Preventing neuronal edema increases network excitability after traumatic brain injury.

Edema is an important target for clinical intervention after traumatic brain injury (TBI). We used in vivo cellular resolution imaging and electrophysiological recording to examine the ionic mechanisms underlying neuronal edema and their effects on neuronal and network excitability after controlled cortical impact (CCI) in mice. Unexpectedly, we found that neuronal edema 48 hours after CCI was associated with reduced cellular and network excitability, concurrent with an increase in the expression ratio of the cation-chloride cotransporters (CCCs) NKCC1 and KCC2.

Efficient validation of teaching and learning using multiple-choice exams.

One purpose of this study was to quantify, by means of single-format, multiple-choice questions at the beginning and end of the course, the extent to which first-year medical students learn neuroscience material from an introductory course in their curriculum. Compared with their precourse test performance (mean = 41.8%), collectively, the students nearly doubled their grade by the end of the course (mean = 81.

Cardiac effects of hypoxia in the neotenous tiger salamander Ambystoma tigrinum.

The aquatic form of the tiger salamander Ambystoma tigrinum lives in high-altitude ponds and is exposed to a hypoxic environment that may be either chronic or intermittent. In many animal species, exposure to hypoxia stimulates cardiac output and is followed by an increase in cardiac mass. The working hypothesis of the present study was that the hearts of these aquatic salamanders exposed to 10-14 days of 5 % oxygen in a laboratory setting would become larger and would differentially express proteins that would help confer tolerance to hypoxia.

Calcium transport mechanisms in muskrat and rat hearts.

Mammalian hearts experience calcium overload during extreme and prolonged hypoxia and the calcium overload may lead to enzyme activation and cell death. Several calcium transport systems were examined in muskrat hearts and compared to those found in rat hearts to determine if there is a species difference that might be related to the muskrats' superior ability to survive hypoxia. Radiolabeled nitredendipine binding was determined in rat and muskrat hearts to estimate the density of voltage gated calcium channels in surface membranes.

Ischemia and ischemic preconditioning in the buffer-perfused pigeon heart.

Isolated pigeon hearts were perfused with Krebs-Henseleit bicarbonate buffer with 1.25 mM Ca++ at a pressure of 60 cm H2O and paced at 210 beats per min. After an equilibration perfusion of 30 min, hearts were subjected to 10 min global ischemia and then reperfused for 30 min.

Hypoxia and ischaemia in buffer-perfused toad hearts.

Previous studies on the effects of ischaemia or hypoxia in ectothermic vertebrate hearts have generally used preparations that were not performing at physiological levels of pressure and flow. The conclusions that ischaemia or hypoxia are not stressful to these organisms were examined in another species, Bufo marinus, in which a buffer-perfused heart was performing physiological levels of work. The in situ preparation demonstrated the Frank-Starling relationship and mechanical characteristics similar to the hearts of intact animals.

Comparison of the responses to hypoxia, ischaemia and ischaemic preconditioning in wild marmot and laboratory rabbit hearts.

Marmots (Marmota flaviventris) are burrowing mammals that may be subjected to low levels of oxygen and high levels of carbon dioxide in their underground environment. Since marmots successfully deal with this physiological challenge, we hypothesized that the isolated perfused marmot heart would be damaged less and recover better from a bout of induced hypoxia or ischaemia than would the heart of a comparison animal, the New Zealand laboratory rabbit (Oryctolagus cuniculus). Isolated marmot and rabbit hearts were made hypoxic by a 30 min perfusion with an oxygen-deficient buffer.

The effect of ATP-sensitive potassium channel modulation on heart rate in isolated muskrat and guinea pig hearts.

Muskrats (Ondontra zibethicus) are common freshwater diving mammals exhibiting a bradycardia with both forced and voluntary diving. This bradycardia is mediated by vagal innervation; however, if hypoxia is present there may be local factors that also decrease heart rate. Some of these local factors may include ATP-sensitive potassium channel activation and extracellular accumulation of potassium ions, hydrogen ions and lactate.

Effect of adenosine on heart rate in isolated muskrat and guinea pig hearts.

The purpose of this study was to compare the responses of isolated hearts of the diving muskrat with the nondividing guinea pig (GP) to determine the contribution of adenosine (ADO) to the profound bradycardia that was seen in isolated muskrat hearts during exposure to hypoxia. Muskrat hearts were more sensitive than GP hearts to the heart rate-lowering effects of exogenously applied ADO or a stable ADO analogue, (R)-N6-(phenylisopropyl)adenosine. The hearts of both species were unpaced, and the bradycardia appeared to be due to high degree of atrioventricular block.

Influence of ATP-sensitive potassium channel blocker on hypoxia-induced damage of isolated guinea pig heart.

1. Isolated guinea pig hearts were perfused under constant flow conditions with Krebs-Henseleit buffer. Hearts were subjected to 15 min of hypoxia followed by reoxygenation in the presence and in the absence of 100 microns glyburide, an ATP-sensitive potassium channel blocker.

Calcium uptake by mitochondria isolated from muskrat and guinea pig hearts.

Subsarcolemmal and interfibrillar mitochondria were isolated from the hearts of the diving muskrat and non-diving guinea pig and direct and indirect measurements of calcium uptake were examined in vitro. The calcium-stimulated respiration rate and 45Ca uptake were measured and found to be greater in muskrat than in guinea pig mitochondria. Muskrat mitochondria were able to endure a greater external calcium concentration than guinea pig mitochondria before exhibiting indications of inner membrane damage.

Comparison of respiration in rat, guinea pig and muskrat heart mitochondria.

1. Subsarcolemmal and interfibrillar mitochondria were isolated from the hearts of the diving muskrat and non-diving guinea pig and rat. Respiration rates, respiratory control ratio (RCR) and phosphorous to oxygen (P:O) ratios determined.

The density of beta-adrenoreceptors in cardiac muscle membranes of muskrats and guinea pigs.

1. Cardiac membranes were prepared and then incubated with a range of concentrations of the beta-adrenergic ligand, dihydroalprenolol. Specific binding to the receptor was measured and receptor density and binding affinities were determined.

Glucose oxidation and oxygen consumption of isolated guinea pig and muskrat hearts.

Glucose in Krebs-Henseleit buffer was presented to isolated Langendorff perfused muskrat and guinea pig hearts that were paced at 240 beats/min. Glucose uptake (amount removed from the perfusion fluid) was 3 times greater in the muskrat hearts than in the guinea pig heart. Glucose oxidation (amount converted to CO2) and oxygen consumption did not differ in the hearts of the two species.

Effect of exercise on uterine blood flow in the pregnant Pygmy goat.

Pygmy goats in the last third of pregnancy were trained to walk on a treadmill at rates up to 2.0 mph and up an inclination of 0-15 degrees. Electromagnetic flowmeters were placed unilaterally on a uterine artery, and measurements were made while the goats were standing quietly on the treadmill and during 5 min of exercise.

Comparison of the response of muskrat, rabbit, and guinea pig heart muscle to hypoxia.

Papillary muscles were removed from anesthetized muskrats and rabbits and mounted in a muscle chamber maintained at 29 degrees C. Muscles were stimulated at a rate of 12/min and subjected to 30 min of hypoxia followed by 30 min of reoxygenation. Peak tension in muskrats declined less than peak tension in rabbits during oxygen deprivation.

Cardiovascular adjustments to laboratory diving in beavers and nutria.

Beavers (Castor canadensis) and nutria (Myocastor coypus) were anesthetized with halothane and catheters placed in the left ventricle, aorta and pulmonary artery, right ventricle or right atrium. The animals were strapped to a board and following recovery from anesthesia the following measurements were taken: regional distribution of blood flow, cardiac output, O2 consumption, arterial and venous blood gases, and pH. The animal was then immersed in 15-20 degrees C water for up to 2.

Arteriovenous malformation of the mandible.

Large intraosseous arteriovenous malformations (AVM) of the mandible are rare lesions. A review of the American literature has revealed sixty cases involving the mandible. This article presents a case of left mandibular AVM in which the initial treatment was embolization.

Countercurrent blood vessel arrangement in beaver (Castor canadensis).

The vascular anatomy of five beavers (Castor canadensis) was studied by dissection and injection of arteries and veins with vinyl acetate. There is extensive countercurrent arrangement of arteries and veins distal to and including the common iliac artery and veins. Two types of countercurrent vessels occur (1) a venae comitantes type in which two or three veins surround a central artery, and (2) a modified rete type.

Verruciform xanthoma. First case reported in a black person.

The twenty-sixth case of verruciform xanthoma is reported. The clinical and light microscopic findings in this case are similar to those previously described of a shaggy, parakeratin-covered, pebbly, or verrucous surface and elongated rete pegs which extend a uniform depth into the underlying conncetive tissue. Large "foam cells" or xanthoma cells filled only the connective tissue papillae between the epithelial pegs.