Basal turn cochleostomy via the middle fossa route for cochlear implant insertion

OBJECTIVE

The current article describes the surgical technique and the very preliminary results of insertion of a cochlear implant, via the middle fossa (MF), in patients with middle ear disease.

STUDY DESIGN

The study design was a case report and a description of surgical technique.

SETTING

The study was conducted at an ENT Department, University of Verona, Verona, Italy.

PATIENTS

Two subjects with profound bilateral hearing loss, the first one presenting a bilateral radical mastoidectomy cavity and the second one with fibroadhesive otitis media, were operated on via the current technique.

INTERVENTION

After adequate exposure of the MF floor, a triangular bony area between the greater superficial petrous nerve and the projection of the labyrinthine portion of the facial nerve was drilled out. The basal cochlear turn facing the middle cranial fossa floor was easily encountered, a small cochleostomy measuring 1 1/2 mm in diameter was performed on the most superficial part of the basal turn, and the electrode carrier was inserted into the fenestrated cochlea. The receiver-stimulator was positioned on a bone well drilled previously in the temporal squama.

MAIN OUTCOME MEASURES

The activity of the inserted electrodes was tested by means of telemetry and intraoperative recording of the electrically evoked auditory responses. Speech perception tests, performed 15 and 30 days after cochlear implant activation, showed a remarkable improvement in the outcomes versus the preoperative values that are provided for comparison.

CONCLUSIONS

This new surgical approach to cochlear implant insertion via the MF route allows stimulation of part of the basal and the middle and apical areas of the cochlea, where greater survival rates of spiral ganglion cells are observed. Cochlear implant insertion via the MF approach represents a promising technique for auditory rehabilitation of subjects with a bilateral radical mastoidectomy cavity, patients suffering from middle ear malformations or chronic middle ear disease due to eustachian tube dysfunction, or subjects with doubtful responses to promontory stimulation.

In vitro study of the NS2-3 protease of hepatitis C virus

Processing at the C terminus of the NS2 protein of hepatitis C virus (HCV) is mediated by a virus-encoded protease which spans most of the NS2 protein and part of the NS3 polypeptide. In vitro cotranslational cleavage at the 2-3 junction is stimulated by the presence of microsomal membranes and ultimately results in the membrane insertion of the NS2 polypeptide. To characterize the biochemical properties of this viral protease, we have established an in vitro assay whereby the NS2-3 protease of HCV BK can be activated posttranslationally by the addition of detergents. The cleavage proficiency of several deletion and single point mutants was the same as that observed with microsomal membranes, indicating that the overall sequence requirements for proper cleavage at this site are maintained even under these artificial conditions. The processing efficiency of the NS2-3 protease varied according to the type of detergent used and its concentration. Also, the incubation temperature affected the cleavage at the 2-3 junction. The autoproteolytic activity of the NS2-3 protease could be inhibited by alkylating agents such as iodoacetamide and N-ethylmaleimide. Metal chelators such as EDTA and phenanthroline also inhibited the viral enzyme. The EDTA inhibition of NS2-3 cleavage could be reversed, at least in part, by the addition of ZnCl2 and CdCl2. Among the common protease inhibitors tested, tosyl phenylalanyl chloromethyl ketone and soybean trypsin inhibitor inactivated the NS2-3 protease. By means of gel filtration analysis, it was observed that the redox state of the reaction mixture greatly influenced the processing efficiency at the 2-3 site and that factors present in the rabbit reticulocyte lysate, wheat germ extract, and HeLa cell extract were required for efficient processing at this site. Thus, the in vitro assay should allow further characterization of the biochemical properties of the NS2-3 protease of HCV and the identification of host components that contribute to the efficient processing at the 2-3 junction.

Chimeric Sindbis viruses dependent on the NS3 protease of hepatitis C virus

The hepatitis C virus (HCV) NS3 protease cleaves the viral polyprotein at specific sites to release the putative components of the HCV replication machinery. Selective inhibition of this enzyme is predicted to block virus replication, and NS3 is thus considered an attractive candidate for development of anti-HCV therapeutics. To set up a system for analysis of NS3 protease activity in cultured cells, we constructed a family of chimeric Sindbis viruses which carry sequences coding for NS3 and its activator, NS4A, in their genomes. HCV sequences were fused to the gene coding for the Sindbis virus structural polyprotein via an NS3-specific cleavage site, with the expectation that processing of the chimeric polyprotein, nucleocapsid assembly, and generation of viable viral particles would occur only upon NS3-dependent proteolysis. Indeed, the chimeric genomes encoding an active NS3 protease produced infectious viruses in mammalian cells, while those encoding NS3 inactivated by alanine substitution of the catalytic serine did not. However, in infected cells chimeric genomes recombined, splicing out HCV sequences and reverting to pseudo-wild-type Sindbis virus. To force retention of HCV sequences, we modified one of the initial chimeras by introducing a second NS3 cleavage site in the Sindbis virus portion of the recombinant polyprotein, anticipating that revertants not encoding an active NS3 protease would not be viable. The resulting chimera produced infectious viruses which replicated at a lower rate than the parental construct and displayed a marked temperature dependence in the formation of lysis plaques yet stably expressed NS3.

Arachidonic acid modulates [14C]stearic acid incorporation into phosphatidylinositol, in human neuroblastoma cells

In the human neuroblastoma cell line SK-N-BE(2), arachidonic acid (AA), supplied in the medium at micromolar concentrations, markedly enhanced [14C]stearic acid (SA) (but not [14C]palmitic acid or [14C]oleic acid) incorporation into phosphatidylinositol (PtdIns). AA failed to stimulate [14C]SA incorporation into PtdIns precursors, namely phosphatidic acid and cytidinediphosphodiacylglycerol: furthermore, enhanced [14C]SA incorporation, brought about by exogenously administered AA, was not restricted to PtdIns tetraenoic species. When cells were pulsed for 1 h with [14C]SA (either in the presence or absence of AA) and then reincubated in AA- and [14C]SA-free medium, a marked loss of radioactivity from PtdIns was observed, that however was restricted to molecular species other than tetraenoic. These results are discussed in the light of possible mechanisms through which PtdIns achieves the 1-stearoyl-2-arachidonoyl configuration.

On the role of agonist-evoked Ca2+ mobilization in sustaining the ongoing phosphoinositide hydrolysis. A study on intact SK-N-BE(2) neuroblastoma cells subjected to muscarinic stimulation

Stimulation of SK-N-BE(2) cells with 1 mM carbachol (Cch) elicited phosphoinositide (PPI) hydrolysis and a rapid elevation of cytosolic Ca2+ concentration ([Ca2+]i) from 115 nM to about 500 nM, followed by a plateau around 200 nM. In myo [3H]inositol-labelled cells, Cch-evoked accumulation of [3H]inositol phosphate (IPs) was not affected when [Ca2+]i was clamped at resting by cell loading with 10 microM BAPTA/AM; under these conditions, maximal 1,4,5-inositol trisphosphate accumulation was not reduced either. When [Ca2+]i was clamped around 700 nM by cell treatment with 600 nM ionomycin, Cch-evoked [3H]IPs accumulation was enhanced by less than 20%, but it was impaired by a 30% and a 55% after [Ca2+]i reduction to about 70 nM and 35-50 nM, by cell loading with 20 microM or 40 microM BAPTA/AM, respectively. These results show that, in SK-N-BE(2) cells, Cch-activated PPI-specific phospholipase C is sensitive to [Ca2+]i but it already operates under suboptimal conditions at resting [Ca2+]i.

Phosphoinositide-derived diacylglycerol conversion to phosphatidic acid is a receptor-dependent and compartmentalized phenomenon in human neuroblastoma

We report that upon muscarinic stimulation of SK-N-BE(2) human neuroblastoma cells, the extent of phosphoinositide-derived diacylglycerol (DG) conversion to phosphatidic acid (PA), operated by a DG kinase, is dependent on the potency of receptor stimulation and correlates with the reduction of phosphatidylinositol 4,5-bisphosphate mass. Evidence is provided that agonist-evoked Ca2+ mobilisation or protein kinase activation are not key events in triggering receptor-generated DG conversion to PA; furthermore, the phenomenon is compartmentalized, namely it occurs within a topologically restricted area that is poorly accessible to DG artificially generated by cell treatment with bacterial phosphatidylinositol-specific phospholipase C. Possible mechanisms driving regulation of the DG kinase operating in the transduction system investigated are discussed.

The NS2 protein of hepatitis C virus is a transmembrane polypeptide

The NS2 protein of hepatitis C virus (HCV) is released from its polyprotein precursor by two proteolytic cleavages. The N terminus of this protein is separated from the E2/p7 polypeptide by a cleavage thought to be mediated by signal peptidase, whereas the NS2-3 junction located at the C terminus is processed by a viral protease. To characterize the biogenesis of NS2 encoded by the BK strain of HCV, we have defined the minimal region of the polyprotein required for efficient cleavage at the NS2-3 site and analyzed the interaction of the mature polypeptide with the membrane of the endoplasmic reticulum (ER). We have observed that although cleavage can occur in vitro in the absence of microsomal membranes, synthesis of the polyprotein precursor in the presence of membranes greatly increases processing at this site. Furthermore, we show that the membrane dependency for efficient in vitro processing varies among different HCV strains and that host proteins located on the ER membrane, and in particular the signal recognition particle receptor, are required to sustain efficient proteolysis. By means of sedimentation analysis, protease protection assay, and site-directed mutagenesis, we also demonstrate that the NS2 protein derived from processing at the NS2-3 site is a transmembrane polypeptide, with the C terminus translocated in the lumen of the ER and the N terminus located in the cytosol.

Effects of perphenazine on the metabolism of inositol phospholipids in SK-N-BE(2) human neuroblastoma cells

Administration of myo-[3H]inositol to SK-N-BE(2) human neuroblastoma cells for 24 hr resulted in equilibrium labelling of phosphatidylinositol (PI), phosphatidylinositol 4-phosphate (PIP) and phosphatidylinositol 4,5-bisphosphate (PIP2), as well as in retention of a large intracellular pool of free myo-[3H]inositol. Equilibrium labelling was no longer observed when cells were treated for 2 hr with 20 microM perphenazine (PPZ) in label-free medium; under these conditions, myo-[3H]inositol from the retained intracellular pool was incorporated into PI and PIP but not into PIP2. Analysis of water-soluble myo-[3H]inositol derivatives and inositol 1,4,5-trisphosphate mass determination indicated that PPZ did not stimulate phosphoinositide hydrolysis by phospholipase C. These results indicate that PPZ raises PI and PIP levels, whereas it is ineffective in expanding the PIP2 pool. The latter effect is not due to a concomitant synthesis and hydrolysis of this lipid.

Muscarinic stimulation of SK-N-BE(2) human neuroblastoma cells elicits phosphoinositide and phosphatidylcholine hydrolysis: relationship to diacylglycerol and phosphatidic acid accumulation

Muscarinic stimulation of the human neuroblastoma cell line SK-N-BE(2) elicits hydrolysis of phosphoinositides and phosphatidylcholine (PtdCho) and produces a rapid and sustained elevation of diacylglycerol (DG) mass. PtdIns(4,5)P2 cleavage by phospholipase C (PLC) occurred immediately after carbachol (CCh) addition, and phosphoinositide hydrolysis was then sustained for at least 5 min. Cell stimulation, after extensive PtdCho labelling by long-term [3H]choline administration, resulted in an enhanced release of [3H]phosphocholine (PCho) into the external medium; enhanced [3H]PCho release, which occurred with a 15 s delay with respect to CCh addition, was particularly pronounced within the first minute of stimulation and proved to be caused by PtdCho-specific PLC activation. In fact, when cells were exposed to [3H]choline for a short period, to extensively label the intracellular PCho pool but not PtdCho, stimulation did not result in an enhanced release of [3H]PCho into the medium. PtdCho-specific phospholipase D (PLD) activation was documented by the accumulation of [3H]phosphatidylethanol in cells prelabelled with [3H]myristic acid and stimulated in the presence of 1% (v/v) ethanol; this metabolic pathway, however, proved to be a minor one leading to generation of phosphatidic acid (PtdOH) during cell stimulation, whereas DG production by the sequential action of PtdCho-specific PLD and PtdOH phosphohydrolase was not observed. Studies on cells which were double-labelled with [3H]myristic acid and [14C]arachidonic acid indicated that within 15 s of stimulation DG is uniquely derived from PtdIns(4,5)P2, whereas PtdCho is the major source at later times. Evidence is provided that rapid and selective conversion of phosphoinositide-derived DG into PtdOH may play an important role in determining the temporal accumulation profile of DG from the above-mentioned sources.

Phenothiazines inhibit acetylcholinesterase by concentration-dependent-type kinetics. A study with trifluoperazine and perphenazine

The properties of perphenazine (PPZ) and trifluoperazine (TFP) as fluorescent dyes were exploited to calculate their critical micellar concentrations. The relative fluorescence quantum yield of the two amphiphiles was dependent on their concentration, abruptly decreasing above 30-40 microM PPZ and 20-30 microM TFP. Evidence is presented that this phenomenon is driven by the formation of non-fluorescent drug aggregates. The type of inhibition kinetics displayed by PPZ and TFP on human erythrocyte acetylcholinesterase (AChE) was also dependent on drug concentration, turning from non-competitive to a "mixed" inhibition type at concentrations at which PPZ and TFP were demonstrated to undergo micelle formation. Results support the notion that phenothiazines may interact with AChE both as monomers and micellar aggregates, producing different inhibitory effects.

Rubidium shows effects different from lithium on phosphatidylinositol metabolism in a cell line of human neuroblastoma

In a SK-N-BE human neuroblastoma cell line the incubation of rubidium (1 and 10 mM) for 24 h significantly increased IP2 formation, whereas it apparently did not affect other inositol phosphates. In comparison to lithium (10 mM), which significantly enhanced inositolmonophosphate and IP2 accumulation following carbamoylcholine (1 mM) stimulation, rubidium at the same concentration, was unable to affect inositol phosphate accumulation. In conclusion, the present experiments show that rubidium, compared with lithium, shows a different profile on phosphoinositide metabolism since its main action is an increase in phosphatidylinositol turnover. These results may have some relevance to the use of rubidium as antidepressant in man.

A study of human erythrocyte acetylcholinesterase inhibition by chlorpromazine

Membrane-bound acetylcholinesterase (AChE) from the human erythrocyte is inhibited by chlorpromazine (CPZ) in a concentration range within this amphiphilic drug has been demonstrated to interact with erythrocyte membranes, causing a large spectrum of physical and structural effects; membrane solubilization with 0.5% Triton X-100 results in a complete loss of CPZ inhibitory potency. Although these observations might suggest a role of membrane lipid environment in mediating human erythrocyte AChE inhibition, we observed that CPZ retains its full inhibitory effect on the fraction of enzyme (5-6% of total) that is solubilized from erythrocytes upon treatment with phosphatidylinositol-specific phospholipase C (PI-PLC) from Bacillus thuringiensis; furthermore, Triton X-100 is able to reverse the CPZ effect also in the case of PI-PLC-solubilized enzyme. These results demonstrate unequivocally that CPZ inhibits human erythrocyte AChE through direct molecular interaction. The inhibition kinetics displayed by CPZ on human erythrocyte AChE are dependent on drug concentration: evidence is provided that this phenomenon may be related to formation of CPZ micellar aggregates.

Hereditary motor and sensory neuropathy type I and type II

In an attempt to clearly identify the different HMSN subgroups, we prospectively evaluated 128 subjects (46 index cases, 39 affected and 43 unaffected relatives) on clinical, genetic and electrophysiological grounds. The diagnosis of HMNS I or II was made in 77 patients. Differential diagnosis between type I and II patients was impossible on clinical grounds alone, but nerve conduction study showed a clear-cut subdivision into two populations. MCV behavior was consistent within families. Inheritance, autosomal dominant in almost all cases, was probably recessive in three HMSN I subjects and pedigree analysis pointed to X-linked transmission in one HMSN I family. We found no evidence for linkage to Duffy locus. We think that similar HMSN phenotypes can be determined by different gene defects. Ulnar nerve F-conduction velocity did not significantly differ from distal MCV in HMSN I: the evidence of a diffuse slowing of nerve conduction supports the hypothesis of a primary myelin defect.

Ca2(+)-dependence of arachidonic acid redistribution among phospholipids of cultured mouse keratinocytes

Mouse keratinocytes cultured in a medium containing less than 0.1 mM Ca2+ (low Ca2+) incorporated [1-14C]arachidonic acid (AA) into phospholipids by kinetics including; (i) a rapid labelling of phosphatidylinositol (PtdIns), phosphatidylserine (PtdSer) and both acid-stable and alkenylacyl forms of phosphatidylcholine (PtdCho); and (ii) a slow but long-lasting radiolabel incorporation into both acid-stable and alkenylacyl forms of phosphatidylethanolamine (PtdEtn), partly associated with a net radioactivity loss from acid stable-PtdCho. Under low Ca2+ conditions no radioactivity transfer apparently occurred between PtdIns and other phospholipid classes. When cells were prelabelled for 24 h with [1-14C]AA and reincubated in label-free medium containing 1.2 mM Ca2+ (normal Ca2+), an early and extensive loss of radioactivity from PtdIns was observed, reasonably in connection with Ca2+ stimulation of phosphoinositide turnover. Cell shift to normal Ca2+ did not result in an increased synthesis of labelled eicosanoids, but was consistent with an increase of radioactivity incorporation into diacylglycerol (DAG) and with a complex pattern of [1-14C]AA redistribution, eventually leading to a marked radioactivity incorporation into acid stable-PtdEtn (but not into alkenylacyl-PtdEtn) and to a labelling decrease of acid stable-PtdCho. The possible mechanisms driving AA recycling after cell shift to normal Ca2+ are discussed.

Arachidonic acid incorporation and redistribution in human neuroblastoma (SK-N-BE) cell phospholipids

The incorporation and redistribution of [1-14C]arachidonic acid in SK-N-BE human neuroblastoma cell phospholipids were investigated. By continuous labelling in serum-enriched medium, a rapid radioactivity incorporation into phosphatidylcholine (PtdCho), phosphatidylinositol, and phosphatidylserine was observed; initially, phosphatidylethanolamine (PtdEtn) was poorly labelled, but at later stages it displayed the highest level of arachidonic acid incorporation, in comparison with other phospholipid classes. Labelling of triacylglycerols was also observed. When cells were pulse-labelled with [1-14C]arachidonic acid and then reincubated in label-free medium, a decrease of the radioactivity in triacylglycerols was observed initially, paralleled by an increase of phospholipid labelling; thereafter, arachidonic acid redistribution was consistent with a net decrease of the radioactivity associated with PtdCho acid-stable forms (i.e., diacyl plus alkylacyl forms), concomitantly with a net labelling increase of both acid-stable PtdEtn and alkenylacyl-PtdEtn. Data indicate the following: (a) neuroblastoma cells incorporate arachidonic acid into phospholipids through complex kinetics involving transfer of the fatty acid from acid-stable PtdCho to both alkenylacyl-PtdEtn and acid-stable PtdEtn; and (b) triacylglycerols act as storage molecules for arachidonic acid which is subsequently incorporated into phospholipids. The possibility that arachidonic acid transfer to PtdEtn subclasses is driven by distinct mechanisms is discussed.

A study of the mechanism by which some amphiphilic drugs affect human erythrocyte acetylcholinesterase activity

The effects of the local anaesthetics procaine, tetracaine and lidocaine and of the antidepressant imipramine on human erythrocyte acetylcholinesterase were investigated. All four amphiphilic drugs inhibited enzymic activity, the IC50 (the concentration causing 50% inhibition) being about 0.40 mM for procaine, 0.05 mM for tetracaine, 0.70 mM for imipramine and 7.0 mM for lidocaine. Procaine and tetracaine inhibited acetylcholinesterase activity competitively at concentrations at which they did not perturb the physical state of the membrane lipid environment, as assessed by steady-state fluorescence polarization, whereas lidocaine and imipramine displayed mixed inhibition kinetics at concentrations at which they induced an enhancement of membrane fluidity. The question was addressed as to whether membrane integrity is a prerequisite for imipramine and lidocaine action. Membrane solubilization by 1% Triton X-100 and a decrease, by dilution, in the detergent concentration to 0.05% [which is above the Triton X-100 critical micelle concentration (c.m.c.)] did not substantially affect the inhibitory potency of the two amphiphilic drugs at their IC50; in the presence of increasing detergent concentrations the inhibitory potency of imipramine was gradually decreased, but not abolished, whereas the inhibitory effect of lidocaine was only slightly diminished, even at 1% Triton X-100. It is suggested that neither competitive nor mixed inhibition kinetics arise from conformational changes of the protein driven by a modification of the physical state of the lipid environment, but from a direct interaction of the amphiphilic drugs with acetylcholinesterase. In particular, the partial loss of the inhibitory potency of imipramine and lidocaine that is observed upon increasing Triton X-100 concentration well above its c.m.c. could be explained in terms of amphiphile partition in detergent micelles and, in turn, of a decreased effective concentration of the two inhibitors in the aqueous phase.

[Hemodynamic status in liver cirrhosis with portal hypertension: a retrospective study on 49 patients]

The Authors report on the data obtained and their evaluation by means of analysis of seven variables and four indices, in 49 cirrhotic patients with portal hypertension and in 10 control patients. Haemodynamic analysis offers the possibility of identifying the dynamic transition stages of a response to stress showing varying degrees of compensation and establishing categories of patients on the basis of cardiovascular and metabolic parameters in relation to liver damage. The Authors, according to Siegel studies, retain that this is a valid method which enables us to obtain useful information on the haemodynamic status of the cirrhotic patient with portal hypertension.

Role of unilateral percutaneous cervical cordotomy in the treatment of neoplastic vertebral pain

The present study is a long-term report on 69 patients undergoing unilateral percutaneous cervical cordotomy for vertebral pain due to neoplastic bone metastases. The pain was unilateral or bilateral and was characterised by a chronic and/or an incident component. Seventy-one per cent (49/69) of the patients benefitted from the operation, obtaining complete, lasting pain relief or a reduced degree of pain, amenable to control by medication with narcotic or non-narcotic drugs. There was a survival Q(50%) of 5 months (S.E. = 1.6) with no pain and a satisfactory quality of life.

Muscle carnitine palmityltransferase deficiency: a case with enzyme deficiency in cultured fibroblasts

A further case of carnitine palmityltransferase (CPT) deficiency in a young man is described, the defect being documented by direct enzyme assays of muscle biopsies. The finding of markedly reduced enzyme activity in the patient's cultured fibroblasts supports the concept that CPT deficiency is a systemic rather than an exclusively muscular condition.

Electroencephalogram in juvenile endemic goiter and in acute goiter

EEG were taken in 27 cases of juvenile endemic goiter and in 5 cases of acute goiter in endemic areas. These conditions, which may be equated nosologically, are virtually always marked by bioelectric changes, which continue even after the thyroid swelling has subsided. In the patients with juvenile endemic goiter the EEG was pathologic in 26 cases (96.3%) and borderline in 1 case. The most frequent changes were theta rhythms at 4–5 cps in 14 cases and at 5–7 cps in 9 other cases. In 3 tracings theta rhythms were associated with delta potentials. In 24 cases potentials with sharp, spike and spike and wave patterns were also present. In all 5 patients presenting acute goiter EEG changes were observed: theta rhythms at 4–5 cps in 1 case, at 5–7 cps in 2 cases and theta rhythms associated with delta waves in 2 other cases. Sharp waves were present in 4 cases. These EEG patterns do not tally with those observed by other workers in so-called primary hyper- and hypothyroidism but they do tally witn those seen in the secondary conditions in which it is accepted that a diencephalohypophyseal disturbance underlies the changes. It is concluded that the EEG both in acute and in juvenile endemic goiter reveals brain signs, regardless of the thyroid function.