Importance of the vestibular system in visually induced nausea and self-vection.

The objective of this study was to determine the importance, if any, of the non-auditory labyrinth of the inner ear in visually induced nausea and self-vection in subjects exposed to a moving visual field with and without concomitant pitching head movements. Subjects treated were 15 normals, 18 unilateral labyrinthectomies and 6 bilateral labyrinthectomies. The findings show a higher incidence of pseudo-Coriolis induced nausea in normal subjects compared to unilateral and bilateral labyrinthectomized subjects. When the subjects were exposed to the moving visual field only (no head movement), pronounced self-vection occurred in all subjects, but with earlier onset in the bilateral labyrinthine defective subjects as compared to normal and unilateral defective subjects. The subjective intensities of self-vections reported by labyrinth-defectives were much more pronounced as compared to normal subjects, and it is apparent that visual input in these subjects achieves much more importance in maintaining compensatory eye movements, and the gain of neck reflexes is enhanced. The findings that visual stimulation is more effective in producing the disabling effects after labyrinthine destruction could possibly be explained by enhancement of vision after loss of labyrinthine sensory input, and the gain in neck reflexes is also enhanced after labyrinthectomy.

Acute hemodynamic effects of atrioventricular pacing at differing sites in the right ventricle individually and simultaneously.

We hypothesized that pacing, which provided a rapid uniform contraction of the ventricles with a narrower QRS, would produce a better stroke volume and cardiac output (CO). We sought to study whether pacing simultaneously at two sites in the right ventricle (right ventricular apex and outflow tract) would provide a narrower QRS and improved CO in 11 patients undergoing elective electrophysiology studies. Patients were studied by transthoracic echocardiography measurement of CO using the Doppler flow velocity method in normal sinus rhythm, AOO pacing (rate 80), DOO pacing in the right ventricular apex (AV delay 100 ms), DOO pacing in the right ventricular outflow tract, and DOO pacing at both right ventricular sites simultaneously in random order. The COs were 5.42 +/- 1.83, 5.61 +/- 1.97, 5.67 +/- 1.6, 5.84 +/- 1.68, and 5.86 +/- 1.52 L/min, respectively (no significant difference by repeated measures analysis of variance [ANOVA]). The QRS durations were 0.09 +/- 0.02, 0.09 +/- 0.02, 0.13 +/- 0.027, 0.13 +/- 0.03, and 0.11 +/- 0.03 secs respectively. Repeated measures ANOVA showed that the QRS duration significantly increased with right ventricular apex or right ventricular outflow tract pacing compared to sinus rhythm and AOO pacing (P < 0.001) but then diminished with pacing at both sites (P < 0.01). QRS duration was not correlated with CO, however the change in QRS duration correlated significantly with the change in CO when pacing was performed at the two right ventricular sites simultaneously. In conclusion, during DOO pacing, there was a trend for pacing in the right ventricular outflow tract or both sites to improve the CO compared to the right ventricular apex. With simultaneous pacing at both ventricular sites, the QRS narrowed. Further studies will be required to see if this approach has value in patients with poor left ventricular function or congestive heart failure.

Determination of structure-activity relationships of Annonaceous acetogenins by inhibition of oxygen uptake in rat liver mitochondria.

A new group of natural compounds, the Annonaceous acetogenins, have recently been determined to inhibit ATP production at a similar site of action and higher levels of potency as rotenone, i.e., at NADH-ubiquinone oxido-reductase, complex I of the mitochondrial electron-transport chain. The acetogenins had earlier been determined to be pesticidal, antimalarial, antimicrobial, anti-parasitic, cytotoxic, and in vivo active as potentially new antitumor agents. In order to determine structural activity relationships (SARs) among these compounds, at the subcellular level, several available acetogenins have been tested. Data obtained, from the inhibition of oxygen consumption by rat liver mitochondria, demonstrated that all of the twenty acetogenins tested are active with IC50 values in the range of 15-800 nM/mg protein. The IC50 value of rotenone was 17 nM/mg protein. The bis-adjacent THF ring acetogenins and the bis-nonadjacent THF ring compounds are about ten times more active than the mono-THF ring acetogenins. Overall, 30-OH and 31-OH-bullatacinone were the most active and were slightly more active than rotenone. The least active were the 4-deoxy bis-adjacent THF ring compounds followed by the mono-THF ring group. There was some variation between the groups, e.g., within the bis-adjacent and mono-THF ring groups, the alpha, beta-unsaturated-gamma-lactones were less active than the keto-lactones, but this observation was reversed for one of the pairs of bis-nonadjacent THF ring acetogenins. Additional hydroxylations, to a maximum of three, seemed to increase activity within all of the groups. Before final decisions on SARs can be made, additional comparisons of the results of this subcellular assay (as an in vitro assay) with the results of in vivo assays should be made. Also, future investigations into the exact site of action within complex I and other possible sites of action (such as the NADH oxidase of plasma membranes) need to be conducted for a more. complete understanding of the utility and potential of this new group of very potent compounds.

Acute pulmonary edema in the post partum and cor triatriatum sinistrum.

A case is described of an apparently healthy young woman in her first pregnancy who presented with acute pulmonary edema in the early postpartum period in the context of mild pregnancy-induced hypertension. After quick improvement in her condition, a Doppler followed by a transesophageal study revealed a left atrial septation with a small atrial septal defect secundum type and moderate mitral regurgitation strongly suggestive of a cor triatriatum sinistrum.

Motion sickness, vascular changes accompanying pseudo-coriolis-induced nausea.

We have previously shown that objective measurements of blood flow changes constitute a useful index in assessing susceptibility to nausea produced by cross-coupled angular accelerations (Coriolis stimulation). The findings of this study confirm the value of using the same technique for assessing the degree of nausea produced by pseudo-Coriolis effects.

Seasickness in totally-enclosed motor-propelled survival craft: remedial measures.

Totally-enclosed motor-propelled survival craft (TEMPSC) are used to evacuate the crews of mobile offshore drilling units in emergencies. The small size and flat bottom of the TEMPSC predispose most occupants to seasickness, even in relatively calm waters. This paper discusses efforts required to improve the well-being of occupants in terms of reducing seasickness, dehydration, hypothermia, anxiety, and the other factors that contribute to loss of comfort and the will to survive. Specific recommendations include the provision of climatic control to regulate temperature, remove odors and provide fresh air; potable water, electrolytes, and survival rations; and an ample supply of motion sickness bags. Overcrowding should be avoided. Anti-motion-sickness drug therapy to control vomiting should be administered in two ways: initial injection of intramuscular scopolamine for fast action followed by a transdermal ear patch for long-term protection. Leadership and seasickness management should be requisite survival training for all oil rig workers.

Seasickness in totally-enclosed motor-propelled survival craft: five offshore oil rig disasters.

Five mobile offshore drilling unit disasters--Alexander L. Kielland, Ocean Ranger, Vinland, Ocean Odyssey, and Rowan Gorilla I--were studied to assess the degree to which seasickness occurs and endangers the lives of occupants of totally-enclosed motor-propelled survival craft (TEMPSC). Thousands of other peacetime marine incidents were reviewed and a literature search was conducted to assess the same seasickness problem. The one reported death in the Vinland abandonment appears to be the only one that could be associated, even remotely, with seasickness. It cannot be established whether or not seasickness contributed to the cause of death in the case of the Ocean Ranger victims, but it did occur in 75% or more of TEMPSC occupants in the other four rig disasters. It has occurred both in relatively calm waters of 1-m wave height and in severe seas of 15-m heights. Evacuees in an intact TEMPSC are able to survive many hours of severe seas; consequently, they should not be rescued until the weather and sea conditions improve. Moreover, practical survival training and good leadership is a principal cornerstone in the amelioration of seasickness.

[Interventional therapy in coronary heart disease]. / Interventionelle Therapie der koronaren Herzkrankheit.

The introduction of balloon angioplasty represents the major step in modern cardiology. Today four different techniques for interventional treatment of coronary artery disease are at our disposition for classic balloon angioplasty, laser balloon, catheter atheromectomy and endovascular prosthesis make interventions in coronary artery disease more easy and reliable. However, the main problem, restenosis, which appears in one fourth of the cases, is not yet resolved. We report our experience in 1000 cases of transluminal approach to coronary artery disease.

Circularvection about earth-horizontal axes in bilateral labyrinthine-defective subjects.

A stationary subject surrounded by a visual display rotating about an earth-horizontal axis typically experiences a sensation of continuous self-rotation (vection) coupled with a paradoxical sensation of a limited degree of body tilt, both opposite to the direction of the stimulus. The sensation of limited body tilt has been attributed to conflict between visually-induced vection, and otolithic and somatosensory graviceptive information which indicates that the body has not moved. We investigated circularvection and illusory body tilt about the horizontal axis in the pitch and roll planes in bilateral labyrinthine-defective (L-D) subjects. Results demonstrated that the bilateral group experienced complete unambiguous self-rotation through an upside-down orientation. The relative contributions of the otolithic and somatosensory graviceptors to visuall-induced tilt is discussed.

Nitrogen narcosis and ethyl alcohol increase the gain of the vestibular ocular reflex.

The effects of air, helium-oxygen (6.4 ATA), and ethyl alcohol (40% by volume at a dose of 1.5 ml/kg body weight) were examined on the gain, number of beats, and phase lag of the vestibular ocular reflex (VOR) by means of electronystagmography (n = 7). It was found that hyperbaric air and alcohol, both alone and in combination, produced approximately the same increase in the velocity of the slow phase component of the nystagmus, thereby elevating the gain of the system to unity. Hyperbaric helium-oxygen did not influence the gain. These findings suggest that nitrogen nacrosis differentially impairs the system controlling the VOR. It is proposed that this impairment may help to explain the disorientation sometimes associated with nitrogen narcosis.

The effects of nitrous oxide on P300 and reaction time.

This experiment investigated the effects of 3 concentrations (15%, 25% and 35%) of nitrous oxide (N2O) on reaction time (RT) and P300 latency and amplitude. Ten subjects responded to visually presented male or female names in an oddball paradigm with accuracy controlled at a high level. The results were analysed on a single-trial basis. Nitrous oxide increased both RT and P300 latency in a dose-related manner and these variables showed a strong between-dose correlation (r = 0.67). Nitrous oxide also decreased P300 amplitude but only up to the 25% dose. The between-dose correlation for P300 amplitude and RT was negligible (r = -0.14). These results suggest that P300 latency is an index of N2O narcosis and are interpreted as indicating that narcosis involves the slowing of stimulus evaluation processes.

Mass correlograms of multiple neuronal activity in the cat's extrastriate cortex.

Electrical activity of a population of visually responsive cells located in the vicinity of a single functionally defined neuron was recorded in the area 18 of the cat's cerebral cortex with a single tungsten microelectrode. The correlograms calculated from the mass activity record showed an existence of a rhythmic neuronal firing with an average interval near to 3 ms. When the system was activated by a visual stimulus, a line at an optimal angle moving in an optimal direction, the rhythmic activity became regular, acquiring an oscillatory sinusoidal character. This rhythmic pattern cannot be easily recognized when the activity of a single neuron is recorded. It is possible that such rhythmic activity involving large numbers of neurons contributes to the recognition of the velocity and position of the visual stimulus.

Lack of homogeneity of receptive fields of visual neurons in the cortical area 18 of the cat.

The receptive fields of "complex" neurons within area 18 of the cerebral cortex of the cat were determined by a computer-assisted method using a moving light bar substantially shorter than the long diameter of the receptive field as a visual stimulus. The visual cells repeatedly generated nerve impulses when the stimulus crossed well-defined "active points" within their receptive fields. Outside of these active points, the cells remained silent. It is suggested that the receptive fields are formed by a discontinuous accumulation of such active points. When the electrical activities of two neighbouring visual neurons are recorded simultaneously, their active points do not coincide. In addition, some active points were located outside the most prominent excitatory part of the receptive field of the studied cells. Individual visual cells typically differ in the number and distribution of active points. Since these cells best respond to a stimulus moving in a certain direction, it is suggested that they may act as direction of movement and/or velocity detectors. Alternate firing of a number of neighboring cells connected to a distributed pattern of peripheral receptors may form a system which is able to code for velocity and direction of the moving stimulus.

Vestibular nuclear neuron activity during active and passive head movement in the alert rhesus monkey.

Responses of single neurons were recorded in the medial and descending vestibular nuclei (MVN and DVN) and in the deep cerebellar nuclei of three juvenile rhesus monkeys (Macaca mulatta). Neuronal activity was measured during both passive sinusoidal and nonsinusoidal whole body rotation (peak velocities were under 90 degrees/s) and during active head movements. Although the active head movements occasionally exceeded 300 degrees/s, most exhibited peak velocities of less than 200 degrees/s. A total of 133 units sensitive to horizontal head rotation were recorded, and of these, 38 were held for sufficient time to obtain both passive and active head movement data. Comparison of the neuronal firing patterns obtained during active and passive head movements revealed no apparent differences. Thus neurons that were observed to burst or pause during saccades with the head fixed continued to do so when the head was free. Both the sensitivity to head velocity and the "inferred" spontaneous firing rate were compared during active and passive head movements by plotting rate-velocity curves for both conditions. When the data points were fitted with linear regression lines, no statistically significant differences in either sensitivity or spontaneous rate were found. The present study provides no evidence that efferent vestibular activity alters the properties of afferent vestibular neurons during active head movements, as has previously been suggested (21). Furthermore, neurons in the rostral portions of the vestibular nuclei in primates encode head velocity based entirely on labyrinthine information. Neither neck proprioceptors nor an efference copy of the head movement motor program seem to contribute significantly to the firing patterns observed.

Circular vection as a function of foreground-background relationships.

It has previously been reported that illusory self-rotation (circular vection) is most effectively induced by the more distant of two moving displays. Experiments are reported in which the relative effectiveness of two superimposed displays in generating circular vection as a function of (i) the separation in depth between them, (ii) their perceived relative distances, and (iii) which display was in the plane of focus was investigated. Circular vection was governed by the motion of the display that was perceived to be the more distant, even when it was actually nearer. However, actual or perceived distance was found to be not the crucial factor in circular vection because even when the distance between the two displays was virtually zero, vection was controlled by the display perceived to be in the background. When the displays were well separated in depth, vection was not affected by whether the near or the far display was in the plane of focus, nor by which display was fixed or pursued by the eyes.

Effects of inert gas narcosis on the vestibular ocular reflex.

A study was conducted to examine the vestibular ocular reflex (VOR) during narcosis. The slow phase velocity of the nystagmus was measured in six subjects by means of electronystagmography during the inhalation of 25% nitrous oxide. It was found that nitrous oxide increased the velocity of the slow phase component of the VOR by approximately 50%. This result indicates that the gain of the VOR is effectively increased during nitrous oxide induced narcosis. It appears that the vestibular end organs and/or the central pathways controlling nystagmus are affected by nitrous oxide and this may be a reason for the disruption in balance associated with inert gas narcosis.

Comparative morphometric study of the vestibular system of the vertebrata: reptilia, aves, amphibia, and pisces.

Morphometric measurements were made from serial sections of the vestibular system in four classes of vertebrates: Reptilia, Aves, Amphibia, and Pisces. Representative species of reptile studied were the lizard (Gekko gecko), the common garter snake (Thamnophis sp.), and the common turtle (Chelonia sp.). The budgie (Melopsittacus undulatas), the common pigeon (Columba domestica), the yellow-bellied sapsucker (Sphyrapicus varius), and the horned owl (Bubo virginianus) were chosen as representative of the bird. For the amphibian, the leopard frog (Rana pipiens), and the mud puppy (Necturus maculatus) were chosen for study. As representative of the fish, the goldfish (Carassius auratus), the tilapia (Tilapia mossambica), the guppy (Lebistes sp.), and the sea horse (Hippocampus sp.) were used in these measurements. The morphometric data obtained were then used in estimates of the time constants in the Steinhausen equation which describes the biophysics of fluid flow in the semicircular canals. In general, the time constants (theta/II in the Steinhausen equation) of these representatives of Reptilia, Aves, and Amphibia were of magnitude similar to those reported in mammals, despite the dissimilarities in the diameters of the ducts, the duct radii of curvature, the dimensions of the cristae ampullares and the utricle, and volumes of endolymph within the vestibular system. However, the short-time constants in Pisces were larger (therefore providing a slower response) than those in other vertebrates, and were similar to that of the turtle and the mud puppy.

Effect of head tilt on visual cortical cell function in the intact and labyrinthectomized cat.

The area of the receptive field, its length and width, its position in the visual field, the peristimulus time (PST) histogram (i.e., the response to successive moving light-bar stimuli), the directional preference, the velocity gradient, and the intertrial (spontaneous) firing rate were studied electrophysiologically in complex cortical visual cells in Brodmann's area 18. These characteristics were explored after head tilt, in immobilized cats, both in intact and in bilaterally labyrinthectomized animals. In intact animals (in 64 cells), most of these characteristics changed after head tilts of 10, 20, 30, or 40 degrees to the right or to the left of the horizontal plane. There was always one specific head position in which the receptive field area was at its smallest. In labyrinthectomized animals (in 29 cells), the lengths, widths, and the areas of the receptive fields were only minimally altered during identical tilts. Similarly, in the labyrinthectomized cats, head tilts (40 degrees, to the right or left) caused no substantial changes in the shape and duration of the PST histogram, compared with those in intact cats. No two visual cortical cells responded to head tilts in exactly the same manner. Such uniqueness in response is probably of importance during visual image analysis; in particular, as it relates to cortical reconstruction of stable visual images during continuously changing head movements and positions.

[Outcome of coronary transluminal angioplasties followed by an occlusion]. / Le devenir des angioplasties transluminales coronariennes suivies d'une occlusion.

Coronary occlusion is the most serious complication of percutaneous transluminal angioplasty. In 440 cases coronary occlusion occurred in 22 patients (5%). Treatment was coronary bypass in 12 cases mechanical recanalization in 7 cases and coronary bypass after unsuccessful mechanical recanalization in 3 cases. One patient died after mechanical recanalization and 9 (41%) had myocardial infarction confirmed by electrocardiography and angiography. The number of coronary occlusions increased initially but decreased with improvements in materials and techniques. It is concluded that coronary occlusion is a severe but rare complication of percutaneous angioplasty. Mechanical recanalization should be attempted, and in case of failure the patient should be referred for surgery. In the large majority of cases the outcome is benign.

Damage to the middle ear and the inner ear in underwater divers.

Postmortem human tissue from recently deceased divers was processed histologically to assess any inner and middle ear damage that could have resulted from the effects of pressure during diving. The following new findings are particularly noteworthy. In one diver, ascent while breath holding resulted in the rupture of the ear drum and blood in the middle ear, in addition to pulmonary barotrauma. In a second diver, following inner ear decompression sickness, new bone growth, similar to that described earlier in experimental studies with the squirrel monkey, was observed in the arms of one of the semicircular canals. These observations are further confirmation that otologic disorders can be a serious threat to divers.