[The mechanisms of hearing and hearing loss]

The ear is constituted of an apparatus for transmission, the external ear and the middle ear, and of an apparatus for perception, the inner ear or cochlea and the acoustic nerves. A disorder can occur at each of these levels, leading to different types of hearing loss: defective transmission through a disorder of the external canal and/or by disorder of the tympanic-middle ear bone apparatus; endocochlear hearing loss through disorder of the ciliary cells of the Corti ganglion and/or by metabolic disorder or by pressure modification (such as Meniere's disease) of the endolymph compartment of the inner ear; retrocochlear hearing loss through disorders of the 8th nerve; central hearing loss through disorder of the temporal cortex.

Distributions of local oxygen saturation and its response to changes of mean arterial blood pressure in the cerebral cortex adjacent to arteriovenous malformations

BACKGROUND AND PURPOSE

To test the hypothesis that neither "steal" as cortical ischemia caused by reduced perfusion pressure nor "breakthrough" on the grounds of loss of pressure autoregulation exist in brain tissue surrounding arteriovenous malformations (AVMs), we established patterns of cortical oxygen saturation (SO(2)) adjacent to AVMs and its behavior after alterations of mean arterial blood pressure.

METHODS

With a microspectrophotometer, SO(2) was scanned in the cortex around AVMs of 44 patients before and after resection and in that of a non-AVM group (n=42) before transsylvian dissection. Autoregulation was evaluated by linear regression analysis after elevation of mean arterial blood pressure (5 microg/min IV noradrenaline). SO(2) values were calculated as medians, percentage of critical values (<25% SO(2)), and coefficients of variance (approximate heterogeneity of SO(2) distributions). All values are given as mean+/-SD.

RESULTS

Forty patients with AVM had an uneventful postoperative course (group A). Four hyperemic complications ("breakthrough") occurred (group B). Autoregulation was tested intact in all groups at all times. Preoperative SO(2) distributions in groups A and C (non-AVMs) were identical. In group B, significantly (P<0.05) lower medians (group A, 52.9+/-16.3%; group B, 44.2+/-17.1%; group C, 51.9+/-11.5% SO(2)), more critical values (group A, 6.5+/-5.1%; group B, 14.7+/-11.1%; group C, 7.1+/-4.9%), and heterogeneous SO(2) distributions (group A, 20.2+/-12.7%; group B, 27.9+/-12.4%; group C, 26.8+/-10.9%) were seen. Increase of median values was significantly higher in group B (76.3+/-10.4% SO(2)) than in group A (65.9+/-13.4% SO(2)) after resection.

CONCLUSIONS

Severely hypoxic areas are uncommon in the cortex adjacent to AVMs and occur predominantly in patients prone to hyperemic complications. Reduced perfusion pressure is compensated in most cases, and moderate hyperemia prevails after excision. Reperfusion into unprotected capillaries of severely hypoxic cortical areas results in "breakthrough," for which vasoparalysis appears not to be the underlying mechanism.

Cellular pathology of hilar neurons in Ammon's horn sclerosis

In addition to functionally affected neuronal signaling pathways, altered axonal, dendritic, and synaptic morphology may contribute to hippocampal hyperexcitability in chronic mesial temporal lobe epilepsies (MTLE). The sclerotic hippocampus in Ammon's horn sclerosis (AHS)-associated MTLE, which shows segmental neuronal cell loss, axonal reorganization, and astrogliosis, would appear particularly susceptible to such changes. To characterize the cellular hippocampal pathology in MTLE, we have analyzed hilar neurons in surgical hippocampus specimens from patients with MTLE. Anatomically well-preserved hippocampal specimens from patients with AHS (n = 44) and from patients with focal temporal lesions (non-AHS; n = 20) were studied using confocal laser scanning microscopy (CFLSM) and electron microscopy (EM). Hippocampal samples from three tumor patients without chronic epilepsies and autopsy samples were used as controls. Using intracellular Lucifer Yellow injection and CFLSM, spiny pyramidal, multipolar, and mossy cells as well as non-spiny multipolar neurons have been identified as major hilar cell types in controls and lesion-associated MTLE specimens. In contrast, none of the hilar neurons from AHS specimens displayed a morphology reminiscent of mossy cells. In AHS, a major portion of the pyramidal and multipolar neurons showed extensive dendritic ramification and periodic nodular swellings of dendritic shafts. EM analysis confirmed the altered cellular morphology, with an accumulation of cytoskeletal filaments and increased numbers of mitochondria as the most prominent findings. To characterize cytoskeletal alterations in hilar neurons further, immunohistochemical reactions for neurofilament proteins (NFP), microtubule-associated proteins, and tau were performed. This analysis specifically identified large and atypical hilar neurons with an accumulation of low weight NFP. Our data demonstrate striking structural alterations in hilar neurons of patients with AHS compared with controls and non-sclerotic MTLE specimens. Such changes may develop during cellular reorganization in the epileptogenic hippocampus and are likely to contribute to the pathogenesis or maintenance of temporal lobe epilepsy.

Social support and the course of bipolar disorder

The current study prospectively examined the impact of social support on symptom severity and recovery from episodes in bipolar disorder, both as a direct influence and as a buffer of life events. Fifty-nine individuals with Bipolar I disorder were followed longitudinally with monthly symptom severity interviews. Social support was measured by the Interpersonal Support Evaluation List and the Interview Schedule for Social Interaction, and life events were assessed using the Life Events and Difficulties Schedule. Individuals with low social support took longer to recover from episodes and were more symptomatic across a 6-month follow-up. Results suggest a polarity-specific effect, in that social support influences depression but not mania. Discussion focuses on theoretical implications of a series of polarity-specific findings within the field.

[Neurofibromatosis type 1 in childhood]

Neurofibromatosis 1 is one of the most common genetic disorders in man. Although almost every body system can be involved, it most frequently affects the skin, the nervous system and the skeleton. Major disease features are café-au-lait spots, axillary/inguinal freckling, neurofibromas and Lisch' nodules. The complications are quite variable, making it impossible to predict the clinical course in an individual patient. To summarize the problems associated with this disease we have quantified manifestations and complications in a group of 38 children with neurofibromatosis 1 who were seen at the University Hospital in Trondheim, Norway between 1987 and 1997. The results are based upon the medical records as well as clinical examination. A wide variety of initial symptoms was recorded, but the majority of the children had café-au-lait spots and axillary/inguinal freckling, two of the seven disease features included in the diagnostic criteria given by the National Institutes of Health. The most frequent complications were tumours, with highest incidence of optic pathway gliomas, disturbances of growth and puberty, delayed psychomotor development and learning disabilities. The risk of complications necessitates regular follow-up in a paediatric department. An annual assessment by an ophthalmologist is also recommended, as well as Visual Evoked Potentials/MRI as screening for optic glioma in children under ten years of age.

Chart documentation of clinical preventive services at 9 Texas clinics

Documentation of clinical preventive services at 9 Texas family practice residency programs, community health centers, and public health regional clinics was examined. Assessment of 11 risks, counseling on those risks, and timeliness of 8 screening tests and immunizations were abstracted. Documentation of clinicians' risk assessment focused on tobacco use (56.4%), alcohol/drug abuse (45.8%), and excess weight (21.6%). Counseling was documented most often for nutrition (20.5%), family planning (11.6%), and physical activity (10.3%). Of the sites studied, public health regional clinics had the highest documentation of assessment and counseling. Community health centers were most up-to-date for diabetes and cholesterol screening. Family practice residencies documented the highest rate of counseling for obesity risk. Clinicians do not document risk assessment, counseling, or up-to-date screening tests and immunizations for most of their adult patients. Texas practitioners may need support or assistance to provide universal access to clinical preventive services.

Efficacy of Glucoprotamin containing disinfectants against different species of atypical mycobacteria

A Glucoprotamin based disinfectant was tested against different strains of atypical mycobacteria in a suspension test. The disinfectant showed maximum detectable kill (> 4 log reduction factor) against all strains tested at 2500 ppm Glucoprotamin within 15 min, except for a glutaraldehyde resistant strain of Mycobacterium chelonae. For the latter, 2500 ppm for 60 min or 5000 ppm for 15 min, were necessary to achieve maximum kill. The glutaraldehyde resistant strain was also resistant to a mixture of different aldehydes.

'Wave-type' structure of a synthetic hexaglycosylated decapeptide: a part of the extracellular domain of human glycophorin A

The three-dimensional structure of a glycopeptide, His-Thr*-Ser*-Thr*-Ser*-Ser*-Ser*-Val-Thr-Lys, with 2-acetamido-2-deoxy-alpha-D-galactose (GalNAc) residues linked to six adjacent amino acids from Thr-10 to Ser-15, was studied by NMR spectroscopy and molecular dynamics (MD) simulations. The hexaglycosylated decapeptide is part of the extracellular domain of human glycophorin A and shows an extended structure of the peptide backbone due to O-glycosylation. Furthermore, each GalNAc residue exhibits one and only one NOE contact from the NHAc proton to the backbone amide proton of the amino acid that the sugar is directly bound to. This indicates a strong preference for the orientation of all GalNAc residues towards the N-terminus. NOE build-up curves were used to determine 42 inter-proton distances that, in connection with phi angles of the peptide backbone obtained from 3J-coupling constants, resulted in constraints for a MD simulation in water. The NMR data and the MD simulations show a preference for an extended backbone structure. The GalNAc residues are located alternatingly on opposite sides of the backbone and reduce the flexibility of the peptide backbone. The conformation of the molecule is relatively rigid and shows a 'wave-type' 3D structure of the peptide backbone within the glycosylation cluster. This new structural element is also supported by the unusual CD spectrum of the glycopeptide.

Health effects of sulfur-related environmental air pollution. II. Cellular and molecular parameters of injury

Recently, concern has been raised about effects related to environmental sulfur and/or acidic aerosols. To assess long-term effects on nonrespiratory lung function, 8 beagle dogs were exposed over a period of 13 mo for 16.5 h/day to a neutral sulfite aerosol at a sulfur(IV) concentration of 0.32 mg m(-3) and for 6 h/day to an acidic sulfate aerosol providing a hydrogen concentration of 15.2 micromol m(-3) for inhalation. Prior to exposure the dogs were kept under clean air conditions for 16 mo to establish physiological baseline values for each animal. A second group of eight dogs (control) was kept for the entire study under clean air conditions. No clinical symptoms were identified that could be related to the combined exposure. Biochemical and cellular parameters were analyzed in sequential bronchoalveolar lavage (BAL) fluids. The permeability of the alveolo-capillary membrane and diethylenetriaminepentaacetic acid (DTPA) clearance was not affected. Similarly, oxidant burden of the epithelial lining fluid evaluated by levels of oxidation products in the BAL fluid protein fraction remained unchanged. Both the lysosomal enzyme beta-N-acetylglucosaminidase and the alpha-1-AT were increased (p <.05). In contrast, the cytoplasmic marker lactate dehydrogenase remained unchanged, indicating the absence of severe damages to epithelial cells or phagocytes. Various surfactant functions were not altered during exposure. Three animals showed elevated levels of the type II cell-associated alkaline phosphatase (AP), indicating a nonuniform response of type II cells. Significant correlations were found between AP and total BAL protein, but not between AP and lactate dehydrogenase, suggesting proliferation of alveolar type II cells. Absolute and relative cell counts in the BAL fluid were not influenced by exposure. Alveolar macrophages showed no alterations with regard to their respiratory burst upon stimulation with opsonized zymosan. The percentage of alveolar macrophages capable of phagocytozing latex particles was significantly decreased (p<.05), while the phagocytosis index was not altered. In view of the results of this and previous studies, we conclude that there is no synergism of effects of these two air pollutants on nonrespiratory lung functions. It is hypothesized that antagonistic effects of these air pollutants on phospholipase A2-dependent pathways account for compensatory physiological mechanisms. The results emphasize the complexity of health effects on lung functions in response to the complex mixture of air pollutants and disclose the precariousness in the risk assessment of air pollutants for humans.

[Quality and identity of terminal care in the hospital exemplified by the SPES VIVA Palliative Project]

In an attempt to contribute to the improvement of fatally ill and dying patients in hospitals, the palliative care project SPES VIVA represents a model scheme by a care concept of contents, personal and spatial definitions [3]. In order to receive an indirect expert verification of success, doctors and nurses of our hospital and of another one were interrogated during the same period. Although we know of the problems inherent in the method, a total of 158 voluntar participants in the study enabled US to compare the results of a preceding poll by W. George et al. of 1988 [2] to prove at least some effects. The SPES VIVA work enhanced the identification of the employed with their work and gave us hints on how to improve the situation of dying patients in our hospital. In comparison with the group of doctors, nurses more often tend to see "too many life-prolongation measures".

A study of speech fractal dimensions

The fractal dimension (D) of a signal gives an estimate of its degree of freedom, which allows estimation of its fluctuations. Using 16 kHz time sampling and the box counting method we studied the Ds of some of the main stationary parts of French speech, the phonemes [a], [e], [i], [o], [y], pronounced 4 times by 10 males and 10 females. Our study demonstrated that the stationary signal of vowels is not fractal, but may, at the smallest scale, provide a kind of signature for each vowel, though the present categorization is not totally significant. Since the box counting method objectifies and quantifies the roughness of the signal, this procedure may be useful for clinical applications. In case of dysphonia, moreover, these signatures could be perhaps be included in the speech signal processing of cochlear implants.

Oxidatively modified proteins in bronchoalveolar lavage fluid of patients with ARDS and patients at-risk for ARDS

Oxidative stress in acute respiratory distress syndrome (ARDS) is considered as an important pathophysiological mechanism in acute impairment of lung function. The present study investigated whether a pulmonary oxidant-antioxidant imbalance is indicated by substantial oxidative modification of proteins in bronchoalveolar lavage (BAL) fluid. Oxidatively modified proteins in BAL fluid, as measured by the reduction of protein carbonyl groups with tritiated borohydride, were studied in control subjects, patients with clinically established ARDS, and patients considered at-risk for ARDS because they had had coronary bypass surgery. Subsets of these at-risk patients were pretreated either with methylprednisolone or N-acetylcysteine. The carbonyl content of BAL fluid proteins was greatly increased in ARDS patients (5.0+/-13 nmol carbonyl x mL(-1) BAL fluid; mean+/-SEM; p=0.0004; n=10) and moderately increased in the untreated patients at-risk for ARDS (1.3+/-0.2 nmol x mL(-1); p=0.027; n=19) compared with controls (0.8+/-0.2 nmol x mL(-1); n=12). The two other at-risk groups pretreated either with methylprednisolone or N-acetylcysteine showed carbonyl values that were statistically not different from the controls (1.2+/-0.2 nmol x mL(-1); p=0.13; n=13, and 1.1+/-0.3 nmol x mL(-1); p=0.40; n=8, respectively). These results show that oxidatively modified proteins clearly accumulated in bronchoalveolar lavage fluid of acute respiratory distress syndrome patients, and to a minor extent in untreated at-risk patients. These data suggest a severe oxidant-antioxidant imbalance in acute respiratory distress syndrome.

The murine Cdx1 gene product localises to the proliferative compartment in the developing and regenerating intestinal epithelium

The mouse Cdx1 gene encodes a homeobox-containing transcription factor and is one of the few homeobox genes known to be expressed in endodermally derived tissues of the intestine in fetal and adult mice. A detailed and systematic study of the expression of the Cdx1 protein was carried out during embryonic intestinal development, postnatal cytodifferentiation and in the regenerating (after radiation-induced damage) intestine of the mouse. Using antibodies directed against Cdx1, we show for the first time that the Cdx1 protein is localised in the proliferating immature epithelium during intestinal development. It becomes restricted to the proliferative crypt compartment during postnatal differentiation, as well as in the adult intestine. The mesenchymal layer was completely negative both during embryonic development and in the postnatal intestine. The expression of the protein was first clearly detected throughout the simple columnar epithelium at day 15 of development. This expression progressively became restricted to the regions of epithelial proliferation in the crypts of the adult mouse by day 40 of post-natal development. There were occasional cells that were Cdx1 positive in the villi. During regeneration of the epithelium after radiation-induced damage, Cdx1 expression diminished during the initial phase of cellular regression. The expression was then very strong in the regenerating epithelial foci, but not in the quiescent sterilised crypts between day 4 and 6. The normal pattern was restored between day 6 and 7. The Paneth cells were negative. The physical segregation of Cdx1 with the proliferative compartment and the hierarchy of cell renewal in the intestinal epithelium is an important example of how regulatory genes function in the maintenance and in the dysfunction of renewing tissues.

Evidence for IL-12-activated Ca2+ and tyrosine signaling pathways in human neutrophils

The cytokine IL-12 is proposed to play a bridging role between innate and adaptive immunity. Here we demonstrate that IL-12 binds specifically to human neutrophils. This binding leads to a transient increase in 1) intracellular free calcium due to its release from membrane-enclosed stores and its influx from extracellular medium, 2) actin polymerization, and 3) tyrosine phosphorylation. IL-12 treatment also leads to a concentration-dependent increase in reactive oxygen metabolite production. The effect of IL-12 is blocked by neutralizing Abs to IL-12. Inhibition of either calcium transient or tyrosine phosphorylation causes inhibition of reactive oxygen metabolite production. However, inhibition of actin polymerization enhances IL-12-induced oxidase activation. Our data suggest 1) a direct role for IL-12 in the activation of human neutrophils, and 2) a calcium-dependent signaling pathway for IL-12.

Slow-growing labyrinthine masses: contribution of MRI to diagnosis, follow-up and treatment

We report the use of MRI in the diagnosis, follow-up and therapeutic management of three cases of intralabyrinthine Schwannoma. The diagnosis was based on the history and initial and follow-up MRI findings. The main feature suggesting the diagnosis was a nodular intralabyrinthine mass of low signal intensity on T2-weighted images, and high or isointense signal on T1-weighted images (relative to cerebrospinal fluid), which showed contrast enhancement. Follow-up imaging showed growth of the tumour in one patient. One patient underwent surgery for severe tinnitus. To detect these lesions, MRI should be focussed on the inner ear, using thin-section T2-weighted and T1-weighted images before and after contrast medium. MRI allowed informed surgical planning.

Different response to balloon angioplasty of carotid and coronary arteries: effects on acute platelet deposition and intimal thickening

PTCA is a well-established intervention to reduce the severity of atherosclerotic coronary stenosis. Its primary success rate is seriously handicapped by the high incidence of late restenosis. Given the clinical and social importance of this proliferative process, new strategies are needed to prevent or reduce restenosis. Several animal models as well as different arteries have been used to study neointimal proliferation after arterial injury. A number of agents have shown to reduce neointimal proliferation after arterial injury in the carotids and iliac arteries of rodent models. Unfortunately, these results have not been replicated in humans. We have compared the acute and late response to vascular injury of the carotid and coronary arteries in the pig. Arterial injury was induced by performing balloon angioplasty of the carotid (elastic) and coronary (muscular) arteries in swine. Acute platelet-thrombus formation was evaluated by quantitation of Indium-labeled platelets deposited on the injured segments 1 h after procedure. Measurement of intimal area was performed by morphometry of the most stenotic cross-section at 28 days after balloon angioplasty. Platelet deposition after mild and severe injury in carotids (4 +/- 1 and 56 +/- 13 x 10(6) platelets/cm2, respectively) and coronaries (15 +/- 5 and 141 +/- 20 x 10(6) platelets/cm2, respectively) are significantly greater in deep, than in mild injury (P < 0.005), and significantly greater in coronary than in carotid arteries after deep injury (P < 0.05). Likewise, late neointima formation was significantly greater (P < 0.05) after mild and severe injury in coronary (17 +/- 0.5 and 56 +/- 2%, respectively) than in carotid arteries (5 +/- 0.5 and 12 +/- 1%, respectively). Acute platelet-thrombus formation and late neointimal thickening are modulated by the degree of injury induced during the interventions; and after disruption of the internal elastic lamina, coronary arteries always had significantly more acute thrombus and neointimal thickening. This study emphasizes the importance of the animal species, the type of injury and the artery chosen for studies on restenosis post interventions.

Alteration of the expression of a plant defensin gene by exon shuffling in bell pepper (Capsicum annuum L.)

We have characterized two members of a gene family encoding defensin-type proteins, j1-1 and j1-2. The structures of these homologous genes are highly similar. Both genes contain an intervening sequence at the same position. Sequence analysis of the intron within the j1-2 gene revealed the existence of an additional exon (exon 2ji) which also encodes a defensin-type protein. It is very likely that this exon was derived by genomic shuffling from a gene, jx, belonging to another subfamily which remains to be characterized. Only transcripts resulting from the splicing of exons 1j2 and 2ji can be detected, indicating that the inserted exon has functionally replaced the original, leaving the latter as a partial pseudogene. This rearrangement did not alter the tissue specificity of expression of the gene j1-2. The corresponding transcripts, present at the stage of fruit set, accumulate progressively during the process of development. In contrast, gene j1-1 is expressed only at the later stages of ripening. Estimates of transcription rates show that in green fruits expression is mainly regulated at a post-transcriptional level, while transcriptional regulation is prominent during ripening.

Can neuronavigation contribute to standardization of selective amygdalohippocampectomy?

Tailored selective amygdalohippocampal resections seem to be an interesting application for neuronavigation. The accuracy of freehand frameless neuronavigation was assessed in 28 patients for its ability to determine the hippocampal resection length, as compared to postoperative MRI. Brain collapse due to CSF displacement caused an expected error of navigation at the brain surface, but almost no error at the tentorial notch. Yet, the hippocampal resection length was overestimated by navigation to an extent of 3 +/- 2 mm. The discrepancy is explained by an anterior-posterior component of brain collapse in a tilted head. Horizontal positioning of the head or navigational marking prior to the occurrence of brain collapse may overcome the problem.

[Persistent facial paralysis: contribution of imaging to identification of perineural infiltrating tumor]

To describe imaging features suggestive of retrograde perineural spread in progressive facial palsy without known tumoral origin. Two reports of perineural infiltration by salivary malignant tumors were diagnosed on abnormal enhancement of the facial nerve associated with an abnormal nerve enlargement (1/2). These unsuspected tumors were located in parotid gland (1/2) and the sub-maxillary gland (1/2). ENT tumors (especially adenoid cystic carcinomas) should be carefully searched in case of perineural spread, as these tumors may be misdiagnosed due to their size, location and signal. Therefore, imaging studies of facial palsy should include temporal bone, skull base, parotid gland, submaxillary gland and sub cutaneous areas of the face. A sub-maxillary gland tumor should be searched in case of facial palsy associated with glossodynia.

[Iatrogenic tinnitus and kophosis treated by cochlear implant. Apropos of a case]

A severe iatrogenic tinnitus has been successfully improved by cochlear implant, despite the hearing and intelligibility of the opposite ear were not profoundly impaired. This case report allows to discuss the eventual enlargement of the classic cochlear implant indications.