Novel ways to modulate the vestibular system: Magnetic vestibular stimulation, deep brain stimulation and transcranial magnetic stimulation / transcranial direct current stimulation.

BACKGROUND: Advances in neurotechnologies are revolutionizing our understanding of complex neural circuits and enabling new treatments for disorders of the human brain. In the vestibular system, electromagnetic stimuli can now modulate vestibular reflexes and sensations of self-motion by artificially stimulating the labyrinth, cerebellum, cerebral cortex, and their connections. OBJECTIVE: In this narrative review, we describe evolving neuromodulatory techniques including magnetic vestibular stimulation (MVS), deep brain stimulation (DBS), transcranial magnetic stimulation (TMS), and transcranial direct-current stimulation (tDCS) and discuss current and potential future application in the field of neuro-otology. RESULTS: MVS triggers both vestibular nystagmic (persistent) and perceptual (lasting ∼1 min) responses that may serve as a model to study central adaptational mechanisms and pathomechanisms of hemispatial neglect. By systematically mapping DBS electrodes, targeted stimulation of central vestibular pathways allowed modulating eye movements, vestibular heading perception, spatial attention and graviception, resulting in reduced anti-saccade error rates and hypometria, improved heading discrimination, shifts in verticality perception and transiently decreased spatial attention. For TMS/tDCS treatment trials have demonstrated amelioration of vestibular symptoms in various neuro-otological conditions, including chronic vestibular insufficiency, Mal-de-Debarquement and cerebellar ataxia. CONCLUSION: Neuromodulation has a bright future as a potential treatment of vestibular dysfunction. MVS, DBS and TMS may provide new and sophisticated, customizable, and specific treatment options of vestibular symptoms in humans. While promising treatment responses have been reported for TMS/tDCS, treatment trials for vestibular disorders using MVS or DBS have yet to be defined and performed.

Correlation between Histopathology and Signal Loss on Spin-Echo T2-Weighted MR Images of the Inner Ear: Distinguishing Artifacts from Anatomy.

BACKGROUND AND PURPOSE: MR imaging of the inner ear on heavily T2-weighted sequences frequently has areas of signal loss in the vestibule. The aim of the present study was to correlate the anatomic structures of the vestibule with areas of low signal intensity. MATERIALS AND METHODS: We reviewed T2-weighted spin-echo MR imaging studies of the internal auditory canal from 27 cases and cataloged signal intensity variations in the vestibulum of inner ears. Using a histologic preparation of a fully mounted human ear, we prepared 3D reconstructions showing the regions of sensory epithelia (semicircular canal cristae, utricular, and saccular maculae). Regions of low signal intensity were reconstructed in 3D, categorized by appearance, and compared with the 3D histologic preparation. RESULTS: The region corresponding to the lateral semicircular canal crista showed signal loss in most studies (94%). In the utricle, a focus of signal loss occurred in the anterior-cranial portion of the utricle and corresponded to the location of the utricular macula and associated nerve on histopathologic specimens (63% of studies). Additional areas of low signal were observed in the vestibule, corresponding to the fluid-filled endolymphatic space and not to a solid anatomic structure. CONCLUSIONS: Small foci of signal loss within the inner ear vestibule on T2-weighted spin-echo images correlate with anatomic structures, including the lateral semicircular canal crista and the utricular macula. More posterior intensity variations in the endolymphatic space are likely artifacts, potentially representing fluid flow within the endolymph caused by magneto-hydrodynamic Lorentz forces.

Vestibular Implant Imaging.

Analogous to hearing restoration via cochlear implants, vestibular function could be restored via vestibular implants that electrically stimulate vestibular nerve branches to encode head motion. This study presents the technical feasibility and first imaging results of CT for vestibular implants in 8 participants of the first-in-human Multichannel Vestibular Implant Early Feasibility Study. Imaging characteristics of 8 participants (3 men, 5 women; median age, 59.5 years; range, 51-66 years) implanted with a Multichannel Vestibular Implant System who underwent a postimplantation multislice CT (n = 2) or flat panel CT (n = 6) are reported. The device comprises 9 platinum electrodes inserted into the ampullae of the 3 semicircular canals and 1 reference electrode inserted in the common crus. Electrode insertion site, positions, length and angle of insertion, and number of artifacts were assessed. Individual electrode contacts were barely discernible in the 2 participants imaged using multislice CT. Electrode and osseous structures were detectable but blurred so that only 12 of the 18 stimulating electrode contacts could be individually identified. Flat panel CT could identify all 10 electrode contacts in all 6 participants. The median reference electrode insertion depth angle was 9° (range, -57.5° to 45°), and the median reference electrode insertion length was 42 mm (range, -21-66 mm). Flat panel CT of vestibular implants produces higher-resolution images with fewer artifacts than multidetector row CT, allowing visualization of individual electrode contacts and quantification of their locations relative to vestibular semicircular canals and ampullae. As multichannel vestibular implant imaging improves, so will our understanding of the relationship between electrode placement and vestibular performance.

Regulation of the Hsp90-binding immunophilin, cyclophilin 40, is mediated by multiple sites for GA-binding protein (GABP).

Within steroid receptor heterocomplexes the large tetratricopeptide repeat-containing immunophilins, cyclophilin 40 (CyP40), FKBP51, and FKBP52, target a common interaction site in heat shock protein 90 (Hsp90) and act coordinately with Hsp90 to modulate receptor activity. The reversible nature of the interaction between the immunophilins and Hsp90 suggests that relative cellular abundance might be a key determinant of the immunophilin component within steroid receptor complexes. To investigate CyP40 gene regulation, we have isolated a 5-kilobase (kb) 5'-flanking region of the human gene and demonstrated that a approximately 50 base pair (bp) sequence adjacent to the transcription start site is essential for CyP40 basal expression. Three tandemly arranged Ets sites within this critical region were identified as binding elements for the multimeric Ets-related transcription factor, GA binding protein (GABP). Functional studies of this proximal promoter sequence, in combination with mutational analysis, confirmed these sites to be crucial for basal promoter function. Furthermore, overexpression of both GABP alpha and GABP beta subunits in Cos1 cells resulted in increased endogenous CyP40 mRNA levels. Significantly, a parallel increase in FKBP52 mRNA expression was not observed, highlighting an important difference in the mode of regulation of the CyP40 and FKBP52 genes. Our results identify GABP as a key regulator of CyP40 expression. GABP is a common target of mitogen and stress-activated pathways and may integrate these diverse extracellular signals to regulate CyP40 gene expression.

Human cyclophilin 40 is a heat shock protein that exhibits altered intracellular localization following heat shock.

The unactivated steroid receptors are chaperoned into a conformation that is optimal for binding hormone by a number of heat shock proteins, including Hsp90, Hsp70, Hsp40, and the immunophilin, FKBP52 (Hsp56). Together with its partner cochaperones, cyclophilin 40 (CyP40) and FKBP51, FKBP52 belongs to a distinct group of structurally related immunophilins that modulate steroid receptor function through their association with Hsp90. Due to the structural similarity between the component immunophilins, FKBP52 and cyclophilin 40, we decided to investigate whether CyP40 is also a heat shock protein. Exposure of MCF-7 breast cancer cells to elevated temperatures (42 degrees C for 3 hours) resulted in a 75-fold increase in CyP40 mRNA levels, but no corresponding increase in CyP40 protein expression, even after 7 hours of heat stress. The use of cycloheximide to inhibit protein synthesis revealed that in comparison to MCF-7 cells cultured at 37 degrees C, those exposed to heat stress (42 degrees C for 3 hours) displayed an elevated rate of degradation of both CyP40 and FKBP52 proteins. Concomitantly, the half-life of the CyP40 protein was reduced from more than 24 hours to just over 8 hours following heat shock. As no alteration in CyP40 protein levels occurred in cells exposed to heat shock, an elevated rate of degradation would imply that CyP40 protein was synthesized at an increased rate, hence the designation of human CyP40 as a heat shock protein. Application of heat stress elicited a marked redistribution of CyP40 protein in MCF-7 cells from a predominantly nucleolar localization, with some nuclear and cytoplasmic staining, to a pattern characterized by a pronounced nuclear accumulation of CyP40, with no distinguishable nucleolar staining. This increase in nuclear CyP40 possibly resulted from a redistribution of cytoplasmic and nucleolar CyP40, as no net increase in CyP40 expression levels occurred in response to stress. Exposure of MCF-7 cells to actinomycin D for 4 hours resulted in the translocation of the nucleolar marker protein, B23, from the nucleolus, with only a small reduction in nucleolar CyP40 levels. Under normal growth conditions, MCF-7 cells exhibited an apparent colocalization of CyP40 and FKBP52 within the nucleolus.

Allelic loss of cyclophilin 40, an estrogen receptor-associated immunophilin, in breast carcinomas.

PURPOSE: Cyclophilin 40 (CyP40) is an estrogen receptor-associated protein which appears to modify receptor function. The aim of this study was to determine the extent of allelic loss at the CyP40 locus in a panel of breast carcinomas using a newly characterized microsatellite marker located upstream of the CyP40 gene and then to correlate this with losses at chromosomal sites for cancer-associated genes. METHODS: Allelic loss at CyP40 was determined from patients' matched tumor and normal breast tissue using Genescan 672 software analysis of fluorescently labeled, PAGE-separated PCR products incorporating the marker. For each patient, allelic loss at CyP40 was then assessed and compared with losses at markers for various cancer-associated genes. RESULTS: Allelic loss was detected in 30% of breast carcinomas from patients heterozygous for the CyP40 marker. All carcinomas demonstrating allelic loss were grade II or III invasive ductal carcinomas and generally showed multiple losses at other sites near known cancer-associated genes. CONCLUSIONS: The polymorphic marker which we characterized was useful in determining allelic loss at the CyP40 locus in breast cancer patients and when applied in these studies in conjunction with various cancer-associated gene markers, suggests that deletions in the region of the CyP40 gene might be a late event in breast tumor progression.

Viruses and virus-like particles in the faeces of dogs with and without diarrhoea.

Negative staining electron microscopy was used to identify viruses in 157 normal and 29 diarrhoeal faecal samples collected from 156 dogs admitted to an animal shelter during an 8 month period (March to October) in 1982. Seven distinct viral types were detected: 21-26 nm parvovirus-like particles, 28-31 nm astrovirus-like particles, a previously undescribed 34-35 nm "round" virus particle, coronavirus, coronavirus-like particles ( CVLP ), rotavirus and papova-like virus. Parvovirus-like particles alone were detected in 14 diarrhoeal and 50 normal faeces, astrovirus-like particles in 3 normal faeces, "round" viruses in 4 normal faeces, coronavirus in 2 diarrhoeal and 5 normal faeces, CVLP in one diarrhoeal and one normal faeces, rotavirus in 2 normal faeces, papova-like virus in one normal faeces, both parvovirus-like particles and coronavirus in 2 diarrhoeal and 2 normal faeces, parvovirus-like particles and rotavirus in one normal faeces and parvovirus-like and papova-like virus in one normal faeces. The significance of these findings in canine and human disease is discussed.

Quasimonochromatic white light fringe interferometer.

Quasimonochromatic light sources, such as laser diodes and high power LEDs, are investigated to determine their suitability for zero path difference determination using white light fringes in a Michelson interferometer. Fringe visibility curves are theoretically determined for various combinations of light sources and compared with experimental results when used in a Michelson interferometer with a 25-m path length. A resolution of 2-3 microm was obtained for a pair of multimode laser diodes and also for a single multimode laser diode operated as an LED. This is more than adequate for the calibration of survey baselines.

Cloning and characterization of a novel caprine genomic repetitive element that hybridizes with papillomavirus DNA.

A goat genomic library was screened by Southern blot hybridization at reduced stringency with a bovine papillomavirus type 5 (BPV 5) DNA probe in order to identify potential cellular and viral sequences related to the papillomavirus genome. A recombinant clone with an 8.5 kb genomic insert was found to contain a 1.3 kb PstI subfragment (designated as P1-1) that hybridized with the DNA of BPV 5, two murine papillomaviruses and human papillomavirus types 5 and 8, but not with DNA from another eight human and bovine papillomavirus types. Southern blot hybridization of the goat P1-1 DNA probe was restricted to a single 1.0 kb subfragment within the E1 open reading frame (ORF) of BPV 5 but produced multiple bands ranging between 1.0 and 9.0 kb when hybridized under stringent conditions with PstI-digested DNA obtained from different goat tissues. The genomic sequence of P1-1 has direct repeats of 10 and 13 nucleotides flanking 153 nucleotides, and 889 nucleotides of sequence, respectively, and an inverted repeat sequence of 11 nucleotides flanking a major ORF potentially coding for 244 residues. Potential splice acceptor and donor sites capable of joining with upstream and downstream exons are present within the major ORF. Sequence similarity between P1-1 and BPV 5 DNA at the nucleotide and amino acid level was limited to a stretch of 58 nucleotides which includes an oligopurine/pyrimidine tract. This region of similarity contains a predicted glutamic acid-rich domain. The P1-1 sequence is a novel repetitive element within the goat genome that is unrelated in sequence to papillomavirus DNA and to genomic sequences of mouse and man.

Recovery of viruses from vegetable surfaces.

The efficiency of a system developed for the recovery of viruses contaminating large quantities of vegetables was investigated in the laboratory and tested in the field. Viruses seeded onto a number of leafy vegetables in the laboratory were eluted with a phosphate-buffered saline solution (pH 9.0). The eluate was clarified by glass wool filtration, and any viruses present were concentrated by adsorption to a Filterite pleated cartridge filter, eluted with 3% beef extract (pH 9.0), and further concentrated by organic flocculation. At least 24 liters of vegetable eluate could be concentrated to 70 to 80 ml, equivalent to a greater than 99.5% reduction in volume. With this system, poliovirus was recovered with a mean efficiency of 58% for all vegetables tested. Adenovirus was recovered from lettuce with a slightly lower mean efficiency (55%). Poliovirus was recovered from large quantities of cabbage for up to 5 days in the field after spray irrigation of relatively low levels of virus, even when heavy rain fell before sampling.

Dynamic range of Ronchi test with a phase-shifted sinusoidal grating.

The dynamic range of a Ronchi test with a phase-shifted sinusoidal grating was investigated theoretically and experimentally. As the number of fringes in a Ronchi interferogram increases, the fringe visibility decreases, which results in a decrease of phase-measurement resolution. It is shown that in order to optimize the dynamic range the effective wavelength of the interferogram should be tuned to the characteristic wavelength of the object wave front. The maximum dynamic range achievable is estimated to be 16 times larger than that of a Fizeau interferometer. Suppressing higher-order diffraction components has achieved sheared interferograms with a signal-to-noise ratio in excess of 60:1. The effects of nonsinusoidal transmittance of the grating and the phase-shift errors were minimized by a seven-sample phase-shifting algorithm, and a phase measurement uncertainty of less than 1/700 has been achieved.

Expression of the estrogen receptor-associated immunophilins, cyclophilin 40 and FKBP52, in breast cancer.

The estrogen receptor alpha (ER alpha) is implicated in the development of breast cancer. The immunophilins, cyclophilin 40 (CyP40) and FKBP52, are associated with ER alpha and other steroid receptors in mutually exclusive heterocomplexes and may differentially modulate receptor activity. Since previous studies have not assessed the levels of these immunophilins in breast cancer, we examined 10 breast cancer cell lines for mRNA and protein expression of CyP40 and FKBP52 and for amplification of the CyP40 gene. In addition, 26 breast carcinomas, including seven with matched normal breast tissue, were examined for mRNA expression of both immunophilins. CyP40 and FKBP52 were ubiquitously expressed in breast cancer cell lines, but there were significant differences in their pattern of expression. FKBP52 protein levels were generally an order of magnitude greater than those for CyP40. FKBP52 mRNA expression correlated strongly with protein expression and was significantly higher in ER alpha-positive compared with ER alpha-negative cell lines. However, CyP40 mRNA expression did not correlate with protein expression, nor did expression of this immunophilin correlate with ER alpha status. Relatively high expression of CyP40 in one cell line (BT-20) could be attributed to amplification of the CyP40 gene. Both immunophilins were also ubiquitously expressed in breast carcinomas, and we demonstrate for the first time that both CyP40 and FKBP52 mRNA are overexpressed in breast tumors compared to matched normal breast controls. The overexpression of CyP40 and FKBP52, coupled with relative differences in their expression in tumors, may have important functional implications for ER alpha and other steroid receptors in breast cancer.

Estradiol-regulated expression of the immunophilins cyclophilin 40 and FKBP52 in MCF-7 breast cancer cells.

The immunophilins, cyclophilin 40 (CyP40) and FKBP52, are associated with the unactivated estrogen receptor in mutually exclusive heterocomplexes and may differentially modulate receptor activity. We have recently shown that CyP40 and FKBP52 mRNA's are differentially elevated in breast carcinomas compared with normal breast tissue. Other studies suggest that such alterations in the ratio of immunophilins might potentially influence steroid receptor function. Studies were therefore initiated to investigate the influence of estradiol on CyP40 and FKBP52 expression in MCF-7 breast cancer cells. Over a 24-h-treatment period with estradiol, CyP40 and FKBP52 mRNA expression was increased approximately five- and 14-fold, respectively. The corresponding protein levels were also elevated in comparison to controls. The antiestrogen, ICI 182,780, was an antagonist for CyP40 and FKBP52 mRNA induction. Cycloheximide treatment did not inhibit this increased immunophilin expression, suggesting that estradiol-mediated activation is independent of de novo protein synthesis. Treatment of MCF-7 cells with estradiol resulted in an increased half-life of both CyP40 and FKBP52 mRNA, as determined by actinomycin D studies. These results suggest that estradiol regulates CyP40 and FKBP52 mRNA expression through both transcriptional and posttranscriptional mechanisms.

Inclusion body myositis: investigation of the mumps virus hypothesis by polymerase chain reaction.

Inclusion body myositis (IBM) is a distinctive form of chronic inflammatory myopathy characterized pathologically by the finding of rimmed vacuoles and 15-18nm microtubular filamentous inclusions in muscle fiber nuclei and cytoplasm. The observation that these filaments resembled nucleocapsids of the paramyxovirus group and showed immunoreactivity with mumps virus (MV) antibodies has led to a long-standing postulate that IBM may be a "slow" mumps infection. We searched for the presence of MV RNA in 34 muscle biopsies (17 frozen and 17 paraffin-embedded) from 18 patients with IBM and 43 control biopsies (mainly from patients with other forms of inflammatory myopathy) using a polymerase chain reaction (PCR). The MV PCR was shown to be sensitive and specific for MV strains (including J-L) and the integrity of muscle RNA extracts was confirmed by PCR detection of constitutive Ableson tyrosine kinase mRNA. MV RNA was not found in any biopsy from the IBM group nor any of the control cases. Our results therefore do not support the mumps hypothesis for IBM.

Influenza in Melbourne, 1982. Epidemiology and virology.

The major features of the outbreaks of influenza A and B, which occurred in Melbourne during the winter of 1982, are described. Diagnoses of influenza A or influenza B were established in 310 patients by virus isolation, immunofluorescence, and serological tests. Immunofluorescence was found to be a valuable, rapid, but considerably less sensitive, test than virus isolation, and serodiagnosis was the test of choice either when patients did not present or when specimens were not collected until late in the illness. The results of haemagglutination-inhibition tests performed with a panel of monoclonal antibodies suggest that at least two recognizably different strains of influenza A and influenza B were circulating in the community.