α-Aminophosphonate inhibitors of metallo-β-lactamases NDM-1 and VIM-2

The upswing of antibiotic resistance is an escalating threat to human health. Resistance mediated by bacterial metallo-β-lactamases is of particular concern as these enzymes degrade β-lactams, our most frequently prescribed class of antibiotics. Inhibition of metallo-β-lactamases could allow the continued use of existing β-lactam antibiotics, such as penicillins, cephalosporins and carbapenems, whose applicability is becoming ever more limited. The design, synthesis, and NDM-1, VIM-2, and GIM-1 inhibitory activities (IC50 4.1-506 μM) of a series of novel non-cytotoxic α-aminophosphonate-based inhibitor candidates are presented herein. We disclose the solution NMR spectroscopic and computational investigation of their NDM-1 and VIM-2 binding sites and binding modes. Whereas the binding modes of the inhibitors are similar, VIM-2 showed a somewhat higher conformational flexibility, and complexed a larger number of inhibitor candidates in more varying binding modes than NDM-1. Phosphonate-type inhibitors may be potential candidates for development into therapeutics to combat metallo-β-lactamase resistant bacteria.

Preparation of Protein-Enriched Outer Membrane Vesicles from Escherichia Coli for In Situ Structural Biology of Outer Membrane Proteins

Bacterial outer membrane vesicles (OMVs) can be selectively enriched with one or more outer membrane proteins to allow the biophysical characterization of these membrane proteins embedded in the native cellular environment. Unlike reconstituted artificial membrane environments, OMVs maintain the native lipid composition as well as the lipid asymmetry of bacterial outer membranes. Here, we describe in detail the steps necessary to prepare OMVs, which contain high levels of a designated protein of interest, and which are of sufficient homogeneity and purity to perform biophysical characterizations using high-resolution methods such as atomic force microscopy, electron microscopy, or single-molecule force spectroscopy.

Antibiotic polymyxin arranges lipopolysaccharide into crystalline structures to solidify the bacterial membrane

Polymyxins are last-resort antibiotics with potent activity against multi-drug resistant pathogens. They interact with lipopolysaccharide (LPS) in bacterial membranes, but mechanistic details at the molecular level remain unclear. Here, we characterize the interaction of polymyxins with native, LPS-containing outer membrane patches of Escherichia coli by high-resolution atomic force microscopy imaging, along with structural and biochemical assays. We find that polymyxins arrange LPS into hexagonal assemblies to form crystalline structures. Formation of the crystalline structures is correlated with the antibiotic activity, and absent in polymyxin-resistant strains. Crystal lattice parameters alter with variations of the LPS and polymyxin molecules. Quantitative measurements show that the crystalline structures decrease membrane thickness and increase membrane area as well as stiffness. Together, these findings suggest the formation of rigid LPS-polymyxin crystals and subsequent membrane disruption as the mechanism of polymyxin action and provide a benchmark for optimization and de novo design of LPS-targeting antimicrobials.

Structural basis of DegP protease temperature-dependent activation

Protein quality control is an essential cellular function mainly executed by a vast array of different proteases and molecular chaperones. One of the bacterial high temperature requirement A (HtrA) protein family members, the homo-oligomeric DegP protease, plays a crucial role in the Escherichia coli protein quality control machinery by removing unfolded proteins or preventing their aggregation and chaperoning them to their final folded state within the periplasm. DegP contains two regulatory PDZ domains, which play key roles in substrate recognition and in the transformation of DegP between inactive hexameric and proteolytic active cage-like structures. Here, we analyze the interaction and dynamics of the DegP PDZ domains underlying this transformation by high-resolution NMR spectroscopy complemented with biochemical cleavage assays. We identify an interdomain molecular lock, which controls the interactions between the two PDZ domains, regulated by fine-tuned temperature-dependent protein dynamics, and which is potentially conserved in proteins harboring tandem PDZ domains.

Architects of their own environment: How membrane proteins shape the Gram-negative cell envelope

Gram-negative bacteria are surrounded by a complex multilayered cell envelope, consisting of an inner and an outer membrane, and separated by the aqueous periplasm, which contains a thin peptidoglycan cell wall. These bacteria employ an arsenal of highly specialized membrane protein machineries to ensure the correct assembly and maintenance of the membranes forming the cell envelope. Here, we review the diverse protein systems, which perform these functions in Escherichia coli, such as the folding and insertion of membrane proteins, the transport of lipoproteins and lipopolysaccharide within the cell envelope, the targeting of phospholipids, and the regulation of mistargeted envelope components. Some of these protein machineries have been known for a long time, yet still hold surprises. Others have only recently been described and some are still missing pieces or yet remain to be discovered.

Preparation of Bacterial Outer Membrane Vesicles for Characterisation of Periplasmic Proteins in Their Native Environment

Bacterial outer membrane vesicles (OMVs) are naturally formed by budding from the outer membrane of Gram-negative bacteria. OMVs consist of a lipid bilayer identical in composition to the original outer membrane and contain periplasmic content within their lumen. Enriched with specific envelope proteins, OMVs make for an excellent native-like platform to study these proteins in-situ using biophysical methods. Here, we describe in detail the preparation of OMVs from Escherichia coli, which are luminally enriched with periplasmic proteins and uniformly labeled with stable isotopes (²H and ¹⁵N), suitable for the subsequent characterisation of proteins at atomic resolution in their native environment by solution-state NMR spectroscopy. The ability to perform structural studies of periplasmic components in-situ clears the way to reaching an in-depth understanding of the functional and mechanistic details of this unique cellular compartment.

High-Resolution In Situ NMR Spectroscopy of Bacterial Envelope Proteins in Outer Membrane Vesicles

The cell envelope of Gram-negative bacteria is an elaborate cellular environment, consisting of two lipid membranes separated by the aqueous periplasm. So far, efforts to mimic this environment under laboratory conditions have been limited by the complexity of the asymmetric bacterial outer membrane. To evade this impasse, we recently established a method to modify the protein composition of bacterial outer membrane vesicles (OMVs) released from Escherichia coli as a platform for biophysical studies of outer membrane proteins in their native membrane environment. Here, we apply protein-enriched OMVs to characterize the structure of three envelope proteins from E. coli using nuclear magnetic resonance (NMR) spectroscopy and expand the methodology to soluble periplasmic proteins. We obtain high-resolution in situ NMR spectra of the transmembrane protein OmpA as well as the periplasmic proteins CpxP and MalE. We find that our approach facilitates structural investigations of membrane-attached protein domains and is especially suited for soluble proteins within their native periplasmic environment. Thereby, the use of OMVs in solution NMR methods allows in situ analysis of the structure and dynamics of proteins twice the size compared to the current in-cell NMR methodology. We therefore expect our work to pave the way for more complex NMR studies of bacterial envelope proteins in the native environment of OMVs in the future.

Mechanical Unfolding and Refolding of Single Membrane Proteins by Atomic Force Microscopy

Atomic force microscopy (AFM)-based single-molecule force spectroscopy allows direct physical manipulation of single membrane proteins under near-physiological conditions. It can be applied to study mechanical properties and molecular interactions as well as unfolding and folding pathways of membrane proteins. Here, we describe the basic procedure to study membrane proteins by single-molecule force spectroscopy and discuss general requirements of the experimental setup as well as common pitfalls typically encountered when working with membrane proteins in AFM.

High-Resolution Imaging of Maltoporin LamB while Quantifying the Free-Energy Landscape and Asymmetry of Sugar Binding

Maltoporins are a family of membrane proteins that facilitate the diffusion of hydrophilic molecules and maltosaccharides across the outer membrane of Gram-negative bacteria. Two contradicting models propose the sugar binding, uptake, and transport by maltoporins to be either symmetric or asymmetric. Here, we address this contradiction and introduce force-distance-based atomic force microscopy to image single maltoporin LamB trimers in the membrane at sub-nanometer resolution and simultaneously quantify the binding of different malto-oligosaccharides. We assay subtle differences of the binding free-energy landscape of maltotriose, maltotetraose, and maltopentaose, which quantifies how binding strength and affinity increase with the malto-oligosaccharide chain length. The ligand-binding parameters change considerably by mutating the extracellular loop 3, which folds into and constricts the transmembrane pore of LamB. By recording LamB topographs and structurally mapping binding events at sub-nanometer resolution, we observe LamB to preferentially bind maltodextrin from the periplasmic side, which shows sugar binding and uptake to be asymmetric. The study introduces atomic force microscopy as an analytical nanoscopic tool that can differentiate among the factors modulating and models describing the binding and uptake of substrates by membrane proteins.

The Periplasmic Chaperones Skp and SurA

The periplasm of Gram-negative bacteria contains a specialized chaperone network that facilitates the transport of unfolded membrane proteins to the outer membrane as its primary functional role. The network, involving the chaperones Skp and SurA as key players and potentially additional chaperones, is indispensable for the survival of the cell. Structural descriptions of the apo forms of these molecular chaperones were initially provided by X-ray crystallography. Subsequently, a combination of experimental biophysical methods including solution NMR spectroscopy provided a detailed understanding of full-length chaperone-client complexes . The data showed that conformational changes and dynamic re-organization of the chaperones upon client binding, as well as client dynamics on the chaperone surface are crucial for function. This chapter gives an overview of the structure-function relationship of the dynamic conformational rearrangements that regulate the functional cycles of the periplasmic molecular chaperones Skp and SurA.

Single-Molecule Force Spectroscopy of Transmembrane β-Barrel Proteins

Single-molecule force spectroscopy (SMFS) has been widely applied to study the mechanical unfolding and folding of transmembrane proteins. Here, we review the recent progress in characterizing bacterial and human transmembrane β-barrel proteins by SMFS. First, we describe the mechanical unfolding of transmembrane β-barrels, which follows a general mechanism dictated by the sequential unfolding and extraction of individual β-strands and β-hairpins from membranes. Upon force relaxation, the unfolded polypeptide can insert stepwise into the membrane as single β-strands or β-hairpins to fold as the native β-barrel. The refolding can be followed at a high spatial and temporal resolution, showing that small β-barrels are able to fold without assistance, whereas large and complex β-barrels require chaperone cofactors. Applied in the dynamic mode, SMFS can quantify the kinetic and mechanical properties of single β-hairpins and reveal complementary insight into the membrane protein structure and function relationship. We further outline the challenges that SMFS experiments must overcome for a comprehensive understanding of the folding and function of transmembrane β-barrel proteins.

Fusion Domains Guide the Oriented Insertion of Light-Driven Proton Pumps into Liposomes

One major objective of synthetic biology is the bottom-up assembly of minimalistic nanocells consisting of lipid or polymer vesicles as architectural scaffolds and of membrane and soluble proteins as functional elements. However, there is no reliable method to orient membrane proteins reconstituted into vesicles. Here, we introduce a simple approach to orient the insertion of the light-driven proton pump proteorhodopsin (PR) into liposomes. To this end, we engineered red or green fluorescent proteins to the N- or C-terminus of PR, respectively. The fluorescent proteins optically identified the PR constructs and guided the insertion of PR into liposomes with the unoccupied terminal end facing inward. Using the PR constructs, we generated proton gradients across the vesicle membrane along predefined directions such as are required to power (bio)chemical processes in nanocells. Our approach may be adapted to direct the insertion of other membrane proteins into vesicles.

The need for community pharmacists in oncology outpatient care: a systematic review

Background One-third of all deaths in Europe each year are attributable to cancer. Issues relating to cancer care, therefore, will continue to expand. To manage the increased challenges-including doctor shortages, an ageing population, and rural distribution of supplies-community pharmacists will likely be required to assume responsibility within oncology care. Aim of the review To assess the need for further investigation into quantity and utility of community pharmacists' interventions in assisting oncology outpatients. Methods Initial search terms for identifying relevant literature within the PubMed database were informed by four key questions. Study selection for the systematic review was performed based on inclusion and exclusion criteria, which were defined a priori using the PICO tool. Literature searches identified 2470 papers, for which titles and abstracts were reviewed. Of these, 220 papers were retained for detailed analysis. The full texts of these manuscripts were then screened by applying the inclusion criteria. The remaining 68 papers were included in the systematic review. Results Several models of pharmacists' interventions in inpatient, medium, and outpatient care have proven to be successful, have been consistently efficacious, and have positively influenced patient outcomes. Importantly, the quantity of scientific research, and thus of reported beneficial outcomes, in outpatient care is much lower than that conducted for inpatient and medium care. Conclusion Based on our findings, we suggest that further investigation of community pharmacists' interventions into oncology outpatient assistance is necessary, and that further research should be conducted to address this need.

Membrane protein distribution in composite polymer-lipid thin films

We present a model system to demonstrate that the positioning of biomolecules (membrane proteins) in a nonnative, complex thin film environment can be regulated by the phase behavior of film components. Partial separation between an amphiphilic polymer and a lipid drives the protein to a fluid phase, mechanically more similar to a cellular bilayer.

Hereditary spherocytosis and other hemolytic anomalies distort diabetic control by glycated hemoglobin

Glycated hemoglobin (%HbA1c) has become a well established and reliable long term parameter indicative of the mean glucose load of the preceding 8 -10 weeks. A normal life span of approximately120 days of the red blood cells (RBC) is an essential condition. Hemolytic affections are characterized by a shorter life span, reducing the overall glucose uptake and %HbA1c. Measured %HbA1c is no longer correlated with mean blood glucose of the preceding period, simulating false low values. Underestimation of this kind is demonstrated for several hemolytic conditions, among them hereditary spherocytosis (HS). This latter, often harmless anomaly may lead to serious underestimation of glucose load. Recent investigations show not only a much higher incidence of HS than hitherto admitted (approximately 1 in 250 persons) but also an abnormally high incidence of diabetes in this hemolytic affection. In the presence of hemolysis %HbA1c is to be interpreted with caution. This justifies systematic detection of HS in routine hematology using--if available--the increase of the percentage of hyperchromic RBC.

HbSC hemoglobinopathy suspected by chest x-ray and red blood cell morphology

Thorax scan was performed for elucidation of a pulmonary problem in a Nigerian immigrant. The aspect of the vertebrae suggested sickle cell disease, of course without specification of the genotype. Routine hematological tests seemed compatible with an HbSC disease, showing typical laboratory features, namely a significant proportion of hyperchromic RBC, corresponding to secondary, non hereditary spherocytosis, presence of numerous target cells and occasional HbC crystals on Pappenheim stained blood films. The diagnosis of HbSC disease was confirmed by HPLC, iso-electric focusing and citrate agar electrophoresis of hemoglobin and by reverse phase HPLC of globin-chains. This case illustrates the importance of screening for hemoglobin anomalies as it is performed in a multiethnic country such as the Grand Duchy of Luxembourg

[Domestic abuse of dementia patients: data collection in a difficult research area]

In the context of a longitudinal dementia caregiver stress study, a short questionnaire was developed in order to assess domestic abuse of dementia patients. By embedding the sensitive topic of domestic violence in a different research context, good compliance in the sample could be achieved which results in high prevalence rates.

Influence of urea on HbA1c-determinations by Menarini HA-8140 and on the difference between immunoturbidimetric and HPLC-HbA1c-results

A secondary peak (#C) included in the HbA1c-calculation by the HA-8140 HPLC (Menarini) shows a fairly good correlation with serum urea. The correlation with HbA1c and with serum glucose is at first glance significant but reveals at a closer look being biased by some incorrect assumptions. The difference between immunoturbidimetric determination (Tinaquant HbA1c II Roche) and HPLC shows a similar behaviour to urea as does the #C-peak of the chromatographic separation. This peak as well as the difference between both determinations of HbA1c could be attributed to carbamylated haemoglobin. The definitive identity has to be proven. This peak could be a monitoring tool for long-time urea. The integration of this peak into total HbA1c by the HA-8140 (Menarini) can lead to a false diagnosis of diabetes in non-diabetic patients with elevated urea.

Multicenter evaluation of the Micral-Test II test strip, an immunologic rapid test for the detection of microalbuminuria

OBJECTIVE

To assess the performance of the Micral-Test II immunologic test strip for the detection of microalbuminuria, a multicenter evaluation in eight European study sites was performed.

RESEARCH DESIGN AND METHODS

Using both the Micral-Test II test strip and the routine method for the determination of albumin concentration, we investigated 2,228 urine samples from diabetic patients. Additionally, interperson variability, color stability, and possible interfering factors (temperature, pH, leucocyturia, erythrocyturia, and drugs) were tested.

RESULTS

For a cutoff concentration of 20 mg/l with respect to the routine methods, a sensitivity of 96.7% and a specificity of 71% were calculated for the Micral-Test II test strip. The negative predictive value was 0.95, and the positive predictive value was 0.78, with a prevalence of positive samples (laboratory method) of 52%. The interperson variability of color interpretation showed 93% concordant readings. The interference study showed an influence of oxytetracycline, leading to higher readings. There was no interference from pH. A sample temperature of < 10 degrees C led to lower readings. In the case of samples with massive leucocyturia and erythrocyturia that may delete the chromatographic process, waiting an additional 1-2 min is needed before reading.

CONCLUSIONS

The results of the multicenter evaluation show that the Micral-Test II test strip permits an immediate and reliable semiquantitative determination of low albumin concentrations in urine samples with an almost user-independent color interpretation.

Screening for oligoalbuminuria by means of Micral-Test II. A new immunological test strip

A new dip-and-read test strip for systematic detection of oligoalbuminuria was assessed. The test is based on a competition for gold-labelled anti-albumin antibodies between specimen albumin and albumin molecules immobilised in the test strip. The final detection area is coloured by excess free antibodies. The colour reaction is compared to a colour scale reflecting 0, 20, 50 and 100 mg/l albumin. Method comparison with an immuno-turbidimetric quantitative technique was performed on 747 unselected specimens. The correlation coefficient was 0.938, the Spearman rank coefficient 0.863. In spite of considerable overlap of the results attributed to the 4 colour blocks, the test was found to be perfectly useful as a 2-class-test, as there were practically no false negative tests and as all the specimens yielding reactions stronger than the 20 mg/l colour block were found to contain 20 mg/l albumin or more by the reference method. The colour block 20 mg/l represents the inevitable grey zone, results in this range being found to be normal and increased above this pathological cut-off by the reference method. Follow-up by quantitative albumin dosage in timed morning urine for all specimens found positive by the dipstick confirms the existence of oligoalbuminuria, eliminating the cases of orthostatic albuminuria, of oligoalbuminuria simulated by low diuresis and the false positives due to oversensitivity of the test strip. The test strip is easy to handle. The reaction time is short and the colour reaction is stable and easy to read. Systematic use of this test in routine urine chemistry is suggested.

Evaluation of the humoral immune response to different antigens in Arkansas Regressor and Progressor chickens

Arkansas Regressor and Progressor chickens were re-evaluated for their immune response to different antigens. Chickens received i.v. injection of either SRBC (10 birds per line) or Salmonella pullorum (SP; 10 birds per line) at 7 wk of age, and sera were collected at 6, 13, and 20 d postimmunization. A third group of birds (10 birds per line) received and i.m. injection of GAT emulsion at 7 and 12 wk of age, and sera were collected at 10 and 14 wk of age. There were significant differences between the two lines in their humoral immunity to SRBC, SP, and GAT. Such results suggest genetic control of humoral immunity to these antigens in these lines. It is unknown whether humoral immunity to these antigens is correlated to regression of tumors induced by Rous sarcoma virus.

Coexistence of two distinct populations of neutrophilic granulocytes, one normal and one partial MPO-deficient

A case of double neutrophilic population in a more or less symptomless patient is described. The diagnosis is made on one hand by the presence of 2 distinct neutrophil clusters on the PEROX display of the H* 1 hematological automate, on the other hand by cytochemical peroxidase staining which clearly confirms the existence of two populations. One of the populations shows normal MPO activity, whereas the second one is characterized by partial MPO deficiency.

Auditory brain stem response monitoring during middle ear surgery

Conductive hearing loss can be determined in the course of middle ear surgery by sound probe stimulation and simultaneous recording of auditory brain stem responses. Mechanical properties of the ossicular chain, usually judged subjectively by the surgeon's visual and tactile senses, can be quantified objectively. Thus, disarticulation of ossicles can be localized precisely, and fixation of the head of the malleus can be differentiated from stapes fixation. Moreover, the function of the reconstructed ossicular chain or prosthesis may be ascertained.

[Is measuring impedance following ear operations an aid in the analysis of postoperative sequelae?]

While the diagnostic value of pre-operative tympanometry is undisputed, there are very few publications on its application in postoperative control of sound conduction development. We measured otoadmittance several times after middle ear surgery in 42 cases. A significant increase of maximal admittance is found over a period of up to 24 months in case of tympanoplasty type I (16 cases, Fig. 1), and after stapedectomy (8 cases, Fig. 3). After a tympanoplasty of type III (Wullsteins classification) many tympanograms were flat, even in the follow-up examination, but a tendency to improvement can also be observed (Fig. 2). In none of the groups was hearing loss correlated with otoadmittance. Thus, tympanometry is not suitable for postoperative evaluation of conductive hearing loss. Nevertheless, our results indicate that the healing process after tympanoplasty modifies middle ear sound transmission for quite a long time.

Conduction of thermal stimuli in the human temporal bone

Temperature changes at different locations in the labyrinth were measured in human temporal bone preparations after syringing with water. In order to simulate physiological conditions, the preparations were placed in a water bath at 37 degrees C. The maximum temperature changes in the horizontal semicircular canal after syringing with temperatures symmetrical to body temperature (44 degrees or 30 degrees C) were found to be clearly asymmetrical (with mean values of 0.6 and -0.3K). From measurements in the external auditory meatus, findings showed that the reference temperature was 34 degrees C in front of the tympanic membrane, which explains the asymmetry recorded. Measurements at different locations showed that the temperature first changes in the regions of the ampullae of the horizontal and the superior semicircular canals. In the vestibule the onset and decay of the temperature change is delayed. The time courses of the temperature difference between locations demonstrate that the temperature difference across the horizontal semicircular canal, which would be responsible for any convective effect in the endolymph, is of shorter duration than the absolute temperature change, which would be responsible for any temperature-mediated volume changes.

[Effect of the stimulus medium--water or air--in thermal evaluation of the vestibular apparatus]

The influence of the stimulus medium in thermal vestibular tests has been investigated by many authors, comparing nystagmus reactions after air and water irrigations. We first measured temperature changes in the ear canal and in the horizontal semicircular canal after both kinds of stimuli, using human temporal bone preparations, which were placed in a water bath of 37 degrees C. Irrigations were done with air of 45 and 27 degrees C with a flow of 5 l/min during 45 s and with 100 ml water of 44 and 30 degrees C during 30 s. The maximum temperature changes in the ear canal are almost equal after both kinds of irrigation (see Figs. 2 and 3). The change of temperature, however, lasts longer after water irrigation. The time constants are 20 and 57 s for the decay after warm and cold water irrigation and 9 and 20 s after air irrigation, respectively. The maximum temperature change in the lateral part of the horizontal semicircular canal is 0.4 and -0.3 degree after warm and cold irrigation with water. The corresponding values after irrigation with air are 0.1 and -0.15 degree. In addition, we investigated the effect of irrigating temporal bone preparations with perforated tympanic membranes (Fig. 4). After irrigation with air of 45 degrees C, the temperature in the horizontal semicircular canal decreased due to evaporation of humidity in the tympanic cavity. The equipment of choice for the irrigation of such ears is a stimulator reported by Scherer, where water flows through a silicon bubble which coats the ear canal.(ABSTRACT TRUNCATED AT 250 WORDS)

Reduced platelet phenylalanine hydroxylating activity in a subgroup of untreated schizophrenics

Considering that platelet phenylalanine hydroxylase represents a rather high percentage of the total body hydroxylating activity, the encountered deficiency may very well be considered as one of the exacerbing factors of psychosis of this type. Further biochemical and clinical characterization of the described subgroup is in progress.

Solvent flow in osmosis and hydraulics: network thermodynamics and representation by bond graphs

A tutorial introduction to network thermodynamics and bond graphs as a modeling technique for any physiochemical system is presented with a particular emphasis on reaction diffusion systems. It combines the generality of nonequilibrium thermodynamics with the advantages of a graph theory. It is applied to the representation of osmotic and hydraulic flows across a semipermeable membrane on the basis of the solvent diffusion theory of osmosis. This theory allows for an easy derivation of the van't Hoff law of osmotic pressure from the Fick law of diffusion. Molar flows and volume flows are transformed into one another by transducers, the modulus of which is the partial molar volume of water, in such a way that power is conserved by a reciprocal transformation between the chemical potential and the pressure. Osmotic and hydraulic resistances are calculated, and their dependence on pore size is estimated.

[Problems with electronic data processing in the practice of an established otorhinolaryngologist]

Theoretically the computer would be a useful tool to help the practitioner with his multiple medical and administrative duties. At present however the modalities of the data input and their poor acceptability for the patient are an obstacle on the way to a wider use of electronic data processing in the physician's office.

A long-term study of hearing in children following neonatal hyperbilirubinemia

We conducted a long-term study of 85 children with known transient neonatal hyperbilirubinemia to determine if their hearing had been affected. None of the children had neural symptoms such as kernicterus. The children ranged in age from birth to 9 months and were studied by means of brainstem evoked response audiometry (BERA). Thirty-four of the children were studied sequentially between 15 and 80 months after the initial examination. Our results showed that there was no significant correlation between serum bilirubin concentrations and BERA thresholds or latencies. These findings indicate that, unlike manifest cases of kernicterus, neonatal hyperbilirubinemia does not affect neonatal hearing when treated promptly.

Experimental investigations on the suitability of the carbon dioxide laser for stapedotomy

Surgery of the footplate may cause a number of possible complications such as cochlear hearing defects or even complete loss of hearing. This has made it necessary to look for improved techniques. When a laser is used for stapedotomy, the energy transmitted to the cochlea must be reduced to the lowest possible level. We thus investigated the carbon dioxide laser to determine whether it would prove to be more advantageous than the argon laser. Animal experiments showed that CO2 laser irradiation is well tolerated. Tests performed on isolated petrous bone resulted in the development of a new surgical instrument suitable for stapedotomy using the CO2 laser. Temperature and pressure measurements were carried out on a simplified model of the human cochlea. Our findings indicated that, with both types of laser, the irradiation required to perforate the otosclerotically thickened footplate adversely affects temperature and pressure development in the cochlea.