Fibrolamellar hepatoma

We found the clinical features of fibrolamellar hepatoma similar to those of nonfibrolamellar hepatoma with the exception of patient age. Although the histopathologic findings of fibrolamellar hepatoma are distinct and easily recognizable, we found that fibrolamellar hepatomas may be histologically heterogeneous. The overall length of survival of patients with fibrolamellar hepatoma was greater than that of patients with nonfibrolamellar hepatoma, but the survival resection was similar, regardless of histologic characteristics. Differences in overall survival between histologic subtypes probably reflects differences in the rate of resectability between fibrolamellar and nonfibrolamellar hepatomas.     

The use of adhesive materials in the conservative restoration of selected posterior teeth

A bstract — The commonly used restorative systems for posterior occlusal restorations by amalgam or cast inlay require removal of sound tooth substance to provide retention, resistance or convenience forms. A better cosmetic result by restricting cavity preparation and using the adhesive properties of glass ionomer cement is described and the results from clinical practice tabulated. This includes a combination system of a surface layer of resin for areas of wear and stress.     

AUTOLOGOUS LYMPHOCYTE THERAPY FOR EXPERIMENTAL CANINE LYMPHOEDEMA: A PILOT STUDY

Obstructive lymphoedema, an accumulation of protein-rich fluid in interstitial spaces, was created in five dogs by a combination of the irradiation of one groin and subsequent surgical ablation of any remaining lymphatics. The lymphoedema was stable for up to 2 years. The aim was to test the efficacy of intra-arterial injection of autologous lymphocytes as a therapy for lymphoedema. The hypothesis was that cytokines produced by lymphocytes mediate proteolysis by macrophage proteinases in the lymphoedematous limb to remove the excess protein and relieve the oedema. A concentrated lymphocyterich preparation was isolated from blood by the Ficoll-Paque method. These preparations were injected into the femoral artery four times at approximately 4 weekly intervals. Three months after the first injection of lymphocytes, lymphoedematous limbs showed a marked 69% reduction in the mean excess circumferences compared with opposite control limbs. After treatment, skin thickness and hydroxyproline content (both measures of fibrosis) as well as water content (a measure of oedema) had reduced significantly. In specimens of interstitial fluid and in skin homogenates acidic proteinase activity increased and the protein concentration decreased significantly compared with controls. It is concluded that increased proteolysis, possibly due to activated macrophages recruited to the lymphoedematous limb, may partly explain these results.     

Altered peripheral and brainstem auditory function in aged rats

A technique for conducting free-field brainstem auditory evoked potential (BAEP) audiometry in unanesthetized, unrestrained rats revealed a non-recruiting 18 dB elevation of click threshold in aged rats. BAEPs were first recorded in young and aged rats to clicks of equal intensity (80 dB SPL). Compared to the young group, aged animals exhibited longer wave I and wave IV latencies with no difference seen in the I–IV central conduction time. The prominent negative wave (No) following wave IV was also delayed and the I-No and IV-No conduction times increased in the aged group. When BAEPs were recorded to clicks with intensities adjusted to 35 dB above individual threshold, no differences in wave I or wave IV latencies or in the I–IV central conduction time were found between groups. However, the No component was delayed and the I-No and IV-No conduction times remained prolonged in the aged group. The results suggest that in addition to changes in peripheral auditory structures, changes in the rostal auditory brainstem accompany age-related hearing loss in rats.     

Multiple brain systems generating the rat auditory evoked potential. I. Characterization of the auditory cortex response

The objectives of this study were to characterize the auditory cortex response in the rat and to examine its contributions to the auditory evoked potentials (AEPs) recorded from the dorsal and lateral skull. This was accomplished by simultaneously recording AEPs from the cortical surface and from skull screw electrodes in anesthetized animals. The initial positive-negative response (P17-N32) was largely restricted to the cortical region corresponding to area 41. More detailed examination of the AEP mapping revealed multiple subcomponents (P9, P14, P17, P19) underlying the initial positivity, with differing topographies. Stimulus-response properties further dissociated the multiple positive subcomponents Reversible local neurochemical suppression confirmed the auditory cortical origin of these AEPs. The auditory cortex-generated AEPs were refractory to barbiturate anesthesia which eliminated all dorsal skull AEPs, indicating that primary auditory cortical AEPs do not make a significant contribution to the dorsal skull-recorded (‘vertex’) AEPs. The findings raise issues regarding multiple parallel auditory processing systems and their associated AEPs.     

Representation of the cochlea within the anterior auditory field (AAF) of the cat

The anterior auditory field (AAF) is a large auditory representation in the cerebral cortex of the cat rostral to the ‘primary’ auditory cortex (AI) on the middle and anterior ectosylvian gyri. Fine-grained microelectrode maps of unit best frequencies were made in AAF of 16 ketamine anesthetized cats. Among the results were the following. (1) Most units in AAF that were driven by tonal stimuli had tuning curves with a single, sharply definable minimum (the best frequency). Occasionally, units were found to have multiple tuning curve minima. (2) In penetrations normal to the cortical surface of AAF, isolated units had remarkably similar tuning curves througout the middle and deep cortical layers. (3) In most of AAF, a restricted sector of the cochlear partition is represented by a straight belt of cortex crossing the entire field. (4) There is a highly ordered representation of the cochlea within AAF. The cortical belt representing the most basal sector of the cochlea (highest best frequencies) is oriented dorsoventrally along the border with the high frequency region of AI. Proceeding rostrally for some distance with AAF, lower frequency cortical belts are parallel to one another and maintain a highly ordered representation of progressively more apical cochlear sectors. The orientation of the lowest frequency representation usually rotates following the ventral curvature of the anterior ectosylvian gyrus. (5) In the portion of the field caudal to the axis of rotation of the representation, best frequency (represented cochlear position) is a simple (and apparently relatively constant) function of distance from the mutual high frequency AI-AAF border. (6) There is a propootionately larger representation of the highest frequency octaves within AAF. (7) The results of penetrations down the banks of the suprasylvian sulcus indicate that there may be units of vertical organization within AAF similar to those in AI, and in somatosensory and visual cortical fields. (8) The boundaries of AAF as well as the frequency representation within it are highly variable when referenced to cortical surface landmarks. (9) The cytoarchitectonic boundaries of AAF approximately correspond with the physiologically defined boundaries. (10) There were no cells driven to discharge by tonal stimuli in the fields dorsal and ventral to AAF.

Comparison of the properties of AAF and AI show that these two fields are remarkably similar in many important features including unit response properties under ketamine anesthesia, short latency to earliest unit discharge, organization in depth, units of vertical organization, size, spatial representation of frequency and proportionately greater representation of higher frequency octaves. They also share some common thalamocortical inputs. These similarities suggest that AAF is not a ‘secondary’ cortical field, but, rather, that AAF and AI are virtually mirror images of one another and are co-participants in the earliest and fundamental processing of acoustic information at the cortical level.