Measurements of the stiffness map challenge a basic tenet of cochlear theories

The cochlear frequency map is believed to depend on the progressive decrease in partition stiffness from base to apex. Measurements on cochleae from human cadavers by von Békésy (1960) suggested that the elasticity of the partition increases by a factor of 100 from the stapes to the helicotrema. However, conventional models require a factor of nearly 10,000 to support the frequency range of normal hearing if entirely determined by partition stiffness. To test this assumption, we measured point stiffness along the width and length of the partition in the gerbil cochlea. Two major findings result from this study: (1) contrary to von Békésy's results, both cellular and extracellular elements of the sensory epithelium exhibit stiffness gradients; and (2) the stiffness changes by only a factor of 100 over the whole cochlea. Our results imply that present ideas regarding partition vibration need to be significantly revised.     

Complete unloading alone may not adequately protect the left ventricle

BACKGROUND: The benefit of left ventricular (LV) unloading for preserving LV function is commonly accepted, but its efficacy remains incompletely defined. METHODS: We studied the influence of complete LV unloading on LV systolic and diastolic mechanics using an in situ isovolumic preparation with two different coronary perfusion pressures (CPPs) in 12 dogs during prolonged normothermic cardiopulmonary bypass. RESULTS: Multivariate analysis of covariance with time as a covariate revealed that a high CPP (143 +/- 36 mm Hg; n = 6) was associated with better preservation of systolic LV function over time as assessed by LV end-systolic elastance (p < 0.001) and the end-systolic pressure-volume relation physiologic intercept (p < 0.001) compared with a moderate CPP (107 +/- 18 mm Hg; p < 0.005 versus a high CPP by t-test; n = 6). Dobutamine (2 micrograms.kg-1.min-1) improved LV end-systolic elastance (p < 0.005) and LV physiologic intercept (p < 0.01) only in the high-CPP group. Conversely, impaired LV diastolic function (as measured by LV stiffness) was observed (p < 0.001) with a high CPP, but did not change with a moderate CPP. CONCLUSIONS: These observations in canine hearts suggest that complete LV unloading may not preserve LV systolic function adequately over time when CPP is maintained in the accepted clinical range. A higher CPP is required to prevent deterioration over prolonged cardiopulmonary bypass times, but diastolic dysfunction still occurs.     

Orthotics and orthodontics

Many doctors think of orthotics or occlusal splints in connection with temporomandibular joint dysfunction patients and treatments. Few think of occlusal splints or intraoral orthotics in conjunction with orthodontics as diagnostic instruments. This article will demonstrate a close association between intraoral orthotics for diagnostic purposes to establish a functional mandibular-maxillary relationship before or during orthodontic treatment. Orthotics allow the practitioner to establish and maintain a harmony between the joint structures, the muscles and the dentition. Orthotics establish the stable orthopedic relationship prior to orthodontic intervention and thus, the end point of treatment established prior to irreversible corrections and a diagnosis of cause-effect relationships can be determined. Properly relating the mandible to the maxilla allows the opportunity to determine the arch developmental requirements necessary to maintain this functional relationship.     

Risk of unprovoked seizure after acute symptomatic seizure: effect of status epilepticus

The dehydration effect is suggested as a mechanism of anesthetic action of magnetic fields. After half an hour of in vivo exposure in constant magnetic field of white male rats to SMF 0.2 T the dehydration of brain, kidney and liver tissues were detected, the decrease of ouabain binding in 5.10(-9) M concentration was detected in brain, heart, spleen and liver tissues and it was increased in kidney tissue. With prolongation of the exposure time the dehydration of the whole organism was observed.     

Nuclear magnetic resonance measurement of skeletal muscle: anisotrophy of the diffusion coefficient of the intracellular water

Four cases of chiasmal syndrome resulting from chromophobe adenoma with normal-sized sella turcica are reported. The predominantly suprasellar growth of these tumors was probably the result of a well-pneumatized sphenoid sinus and/or a congenitally deficient diaphragma sellae. In patients with chiasmal syndrome, a high suspicion of a surgically treatable lesion must be maintained in spite of radiographs showing a normal-sized sella. In spite of the difficulties presented by normal variations, subtle findings should be searched for on the plain films and given additional weight in the patient with a chiasmal syndrome. An aggressive diagnostic work-up, including pneumoencephalography with thin-section tomography, should be pursued in all such patients before accepting some alternate explanation, such as demyelinating disease, for visual impairment.     

Reactions of vitamin E and its model compound 2,2,5,7,8-pentamethylchroman-6-ol with ozone

A system has been developed to determine intraocular tumor volume, a characteristic that has been estimated in previous studies from linear dimensions using a variety of models. Volume was determined by tracing tumor boundaries in sequential, parallel ultrasound scans, adding the areas and multiplying by the interslice interval. The in vitro accuracy of the technique was within +/- 2%. The mean difference between volumes determined from replicate in vivo scans of intraocular tumors was 4.3%. Serial scan volumes were, on average, 19% smaller than volumes computed from an ellipsoidal model and 13% smaller than area-rotational volumes. Differences of as much as 50% were observed between serial scan volumes and volumes computed with these models. The results indicate that methods based on either linear measurements or the tumor area in a single cross-section will tend to both systematically overestimate tumor volume and suffer from unpredictable, nonsystematic errors.