Osteoporosis, bisphosphonate use, and risk of moderate or worse hearing loss in women

BACKGROUND

Osteoporosis and low bone density (LBD) may be associated with higher risk of hearing loss, but findings are inconsistent and longitudinal data are scarce. Bisphosphonates may influence risk, but the relation has not been studied in humans. We longitudinally investigated associations of osteoporosis and LBD, bisphosphonate use, vertebral fracture (VF), hip fracture (HF), and risk of self-reported moderate or worse hearing loss.

DESIGN

Longitudinal cohort study.

SETTING

The Nurses' Health Study (NHS) (1982-2016) and Nurses' Health Study II (NHS II) (1995-2017).

PARTICIPANTS

Participants included 60,821 NHS women, aged 36-61 years at baseline, and 83,078 NHS II women, aged 31-48 years at baseline (total n = 143,899).

MEASUREMENTS

Information on osteoporosis, LBD, bisphosphonate use, VF, HF, and hearing status was obtained from validated biennial questionnaires. In a subcohort (n = 3749), objective hearing thresholds were obtained by audiometry. Multivariable-adjusted Cox proportional hazards models were used to examine independent associations between osteoporosis (NHS), osteoporosis/LBD (NHS II), and risk of hearing loss.

RESULTS

The multivariable-adjusted relative risk (MVRR, 95% confidence interval) of moderate or worse hearing loss was higher among women with osteoporosis or LBD in both cohorts. In NHS, compared with women without osteoporosis, the MVRR was 1.14 (1.09, 1.19) among women with osteoporosis; in NHS II, the MVRR was 1.30 (1.21, 1.40) among women with osteoporosis/LBD. The magnitude of the elevated risk was similar among women who did and did not use bisphosphonates. VF was associated with higher risk (NHS: 1.31 [1.16, 1.49]; NHS II: 1.39 [1.13, 1.71]), but HF was not (NHS: 1.00 [0.86, 1.16];NHS II: 1.15 [0.75,1.74]). Among participants with audiometric measurements, compared with women without osteoporosis/LBD, the mean multivariable-adjusted hearing thresholds were higher (i.e., worse) among those with osteoporosis/LBD who used bisphosphonates.

CONCLUSION

Osteoporosis and LBD may be important contributors to aging-related hearing loss. Among women with osteoporosis, the risk of hearing loss was not influenced by bisphosphonate use.

Prospective Study of Dietary Patterns and Hearing Threshold Elevation

We conducted a prospective study of dietary patterns and longitudinal change in audiometric hearing thresholds among 3,135 women (mean age = 59 years) in the Nurses' Health Study II (2012-2018). Diet adherence scores for the Dietary Approaches to Stop Hypertension (DASH) and Alternate Mediterranean (AMED) diets and the Alternate Healthy Eating Index 2010 (AHEI-2010) were calculated using validated food-frequency questionnaires. Baseline and 3-year follow-up hearing sensitivities were assessed by pure-tone audiometry at 19 US sites. We used multivariable-adjusted logistic regression models to examine independent associations between diet adherence scores and risk of ≥5 dB elevation in the pure-tone average (PTA) of low-frequency (LPTA0.5,1,2 kHz), mid-frequency (MPTA3,4 kHz), and high-frequency (HPTA6,8 kHz) hearing thresholds. Higher adherence scores were associated with lower risk of hearing loss. Compared with the lowest quintile of DASH score, the multivariable-adjusted odds ratios for mid-frequency and high-frequency threshold elevation in the highest quintile were 0.71 (95% confidence interval (CI): 0.55, 0.92; P for trend = 0.003) and 0.75 (95% CI: 0.59, 0.96; P for trend = 0.02); for AMED and AHEI scores, for mid-frequency threshold elevation, they were 0.77 (95% CI: 0.60, 0.99; P for trend = 0.02) and 0.72 (95% CI: 0.57, 0.92; P for trend = 0.002). Nonsignificant inverse associations were observed for high-frequency threshold elevation. There were no significant associations between adherence scores and low-frequency threshold elevation. Our findings indicate that eating a healthy diet might reduce the risk of acquired hearing loss.

Nutritional status and interventions in hospice: physician assessment of cancer patients

BACKGROUND

Cancer cachexia is a multifactorial syndrome characterised by a progressive loss of skeletal muscle mass. It adversely influences quality of life, treatment response and survival. Early identification and multimodal interventions can potentially treat cancer cachexia. However, healthcare professionals demonstrate a lack of understanding and the ability to identify cancer cachexia early. The present study aimed to evaluate the assessment by physicians of nutritional status in cancer patients admitted to hospice.

METHODS

A retrospective medical record review was conducted on all cancer admissions to a specialist in-patient palliative care unit over a 4-month period between October 2016 and January 2017. Charts were reviewed for evidence of documented nutritional assessment by physicians. Data were collected from the referral letter, admission notes, drug kardex and discharge letter. The information extracted included: (i) patient demographics and characteristics; (ii) terms used by physicians to describe nutritional status; (iii) any record of nutritional impact symptoms (NIS) experienced by the patient; and (iv) nutritional interventions prescribed.

RESULTS

One hundred and forty admissions were evaluated. Nutritional terminology and NIS were most commonly documented on the admission notes. Only 41% of documents recorded any nutritional term used by physicians to assess nutritional status. Furthermore, 71% of documents recorded at least one NIS experienced by the patient. Fatigue was the most frequent NIS.

CONCLUSIONS

We identified an inadequate nutritional assessment of cancer patients admitted to hospice. Implementation of a nutritional symptom checklist and nutrition screening tools, along with enhanced physician education and multidisciplinary nutrition care, could improve the identification and management of cancer cachexia in the palliative care setting.

Third-generation bisphosphonates for cochlear otosclerosis stabilizes sensorineural hearing loss in long-term follow-up

Objective

To assess long‐term hearing outcomes in patients treated with third‐generation bisphosphonates for otosclerosis‐related progressive sensorineural hearing loss (SNHL).

Study Design

Retrospective case series review

Methods

We performed a retrospective case series review of patients with otosclerosis and progressive SNHL. Patients were treated with either risedronate or zoledronate after a diagnosis of otosclerosis with a significant SNHL component. Bone conduction pure tone threshold averages (BC‐PTAs) and word recognition scores (WRS) before and after bisphosphonate administration in long‐term follow‐up was analyzed. Significant change in BC‐PTA was defined as greater than 10dB or between 4% and 18% in WRS based on binomial variance.

Results

Seven patients were identified and 14 ears met inclusion criteria. Three patients were female and the mean age was 48.3 ± 10.3 years. The mean duration between treatment with bisphosphonate administration and long‐term post‐treatment follow‐up audiometry was 87.6 ± 18.3 months, with a range of 61.6 to 109.1 months and median of 89.2 months. Analysis using BC‐PTA and WRS demonstrated that 11 ears remained stable while 2 improved and 1 worsened. No patient experienced any major complication as the result of bisphosphonate therapy.

Conclusion

Treatment with third‐generation bisphosphonates is associated with stability in otosclerosis‐related sensorineural hearing over 5‐ to 9‐year period. These results suggest that such medications may prevent the progression of SNHL in patients with otosclerosis.

Level of Evidence

4 (Case series).

Comparison of umbo velocity in air- and bone-conduction

This study investigates the ossicular motion produced by bone-conducted (BC) sound in live human ears. Laser Doppler vibrometry was used to measure air conduction (AC)- and BC-induced umbo velocity (V(U)) in both ears of 10 subjects, 20 ears total. Sound pressure in the ear canal (P(EC)) was measured simultaneously. For air conduction, V(U) at standard hearing threshold level was calculated. For BC, ΔV was defined as the difference between V(U) and the tympanic ring velocity (an estimate of the skull velocity measured in the ear canal). ΔV and P(EC) at BC standard hearing threshold were calculated. ΔV at standard BC threshold was significantly smaller than V(U) at standard AC threshold between 500 Hz and 2000 Hz. Ear canal pressure at BC threshold tended to be smaller than for AC below 3000 Hz (with significant differences at 1000 Hz and 2000 Hz). Our results are most consistent with inertia of the ossicles and cochlear fluid driving BC hearing below 500 Hz, but with other mechanisms playing a significant role at higher frequencies. Sound radiated into the external ear canal might contribute to BC hearing at 3000 Hz and above.

Clinical investigation and mechanism of air-bone gaps in large vestibular aqueduct syndrome

OBJECTIVES

Patients with large vestibular aqueduct syndrome (LVAS) often demonstrate an air-bone gap at the low frequencies on audiometric testing. The mechanism causing such a gap has not been well elucidated. We investigated middle ear sound transmission in patients with LVAS, and present a hypothesis to explain the air-bone gap.

METHODS

Observations were made on 8 ears from 5 individuals with LVAS. The diagnosis of LVAS was made by computed tomography in all cases. Investigations included standard audiometry and measurements of umbo velocity by laser Doppler vibrometry (LDV) in all cases, as well as tympanometry, acoustic reflex testing, vestibular evoked myogenic potential (VEMP) testing, distortion product otoacoustic emission (DPOAE) testing, and middle ear exploration in some ears.

RESULTS

One ear with LVAS had anacusis. The other 7 ears demonstrated air-bone gaps at the low frequencies, with mean gaps of 51 dB at 250 Hz, 31 dB at 500 Hz, and 12 dB at 1,000 Hz. In these 7 ears with air-bone gaps, LDV showed the umbo velocity to be normal or high normal in all 7; tympanometry was normal in all 6 ears tested; acoustic reflexes were present in 3 of the 4 ears tested; VEMP responses were present in all 3 ears tested; DPOAEs were present in 1 of the 2 ears tested, and exploratory tympanotomy in 1 case showed a normal middle ear. The above data suggest that an air-bone gap in LVAS is not due to disease in the middle ear. The data are consistent with the hypothesis that a large vestibular aqueduct introduces a third mobile window into the inner ear, which can produce an air-bone gap by 1) shunting air-conducted sound away from the cochlea, thus elevating air conduction thresholds, and 2) increasing the difference in impedance between the scala vestibuli side and the scala tympani side of the cochlear partition during bone conduction testing, thus improving thresholds for bone-conducted sound.

CONCLUSIONS

We conclude that LVAS can present with an air-bone gap that can mimic middle ear disease. Diagnostic testing using acoustic reflexes, VEMPs, DPOAEs, and LDV can help to identify a non-middle ear source for such a gap, thereby avoiding negative middle ear exploration. A large vestibular aqueduct may act as a third mobile window in the inner ear, resulting in an air-bone gap at low frequencies.

UNTREATED TRANSIENT LONGER THAN 7-DAY CHAT, CIRCADIAN HYPER-AMPLITUDE TENSION, IN A 7-YEAR PERSPECTIVE

The case report presented herein aims at promoting the awareness in medical, notably cardiological, practice of the importance of, first, collecting at least a week-long record of around-the-clock measurements of blood pressure (BP) and heart rate (HR) (and a much longer record if the 7 day record so indicates) and, second, of analysing the data chronobiologically in the light of reference values specified as a function of time, gender and age as a minimum. In addition to diagnosing deviations in a chronome (time structure)-adjusted mean value, a chronobiological approach identifies abnormalities in the variability of BP and/or HR, gauged by the circadian characteristics (double amplitude and acrophase, measures of the extent and timing of predictable change within a cycle) and by the standard deviation. A woman in presumably good health was 60 years of age at the start of intermittent monitoring over a 7 year span. The case report illustrates the extent to which a decision based on single BP readings and even on 24 hour averages may be misleading. Treatment based on an initial week-long monitoring may benefit from continued long-term monitoring.

Strong decrease in lignin content without significant alteration of plant development is induced by simultaneous down-regulation of cinnamoyl CoA reductase (CCR) and cinnamyl alcohol dehydrogenase (CAD) in tobacco plants

Different transgenic tobacco lines down-regulated for either one or two enzymes of the monolignol pathway were compared for their lignin content and composition, and developmental patterns. The comparison concerned CCR and CAD down-regulated lines (homozygous or heterozygous for the transgene) and the hybrids resulting from the crossing of transgenic lines individually altered for CCR or CAD activities. Surprisingly, the crosses containing only one allele of each antisense transgene, exhibit a dramatic reduction of lignin content similar to the CCR down-regulated parent but, in contrast to this transgenic line, display a normal phenotype and only slight alterations of the shape of the vessels. Qualitatively the lignin of the double transformant displays characteristics more like the wild type control than either of the other transgenics. In the transgenics with a low lignin content, the transformations induced other biochemical changes involving polysaccharides, phenolic components of the cell wall and also soluble phenolics. These results show that the ectopic expression of a specific transgene may have a different impact depending on the genetic background and suggest that the two transgenes present in the crosses may operate synergistically to reduce the lignin content. In addition, these data confirm that plants with a severe reduction in lignin content may undergo normal development at least in controlled conditions.

Enabling technologies for manipulating multiple genes on complex pathways

Many complex biochemical pathways in plants have now been manipulated genetically, usually by suppression or over-expression of single genes. Further exploitation of the potential for plant genetic manipulation, both as a research tool and as a vehicle for plant biotechnology, will require the co-ordinate manipulation of multiple genes on a pathway. This goal is currently very difficult to achieve. A number of approaches have been taken to combine or 'pyramid' transgenes in one plant and have met with varying degrees of success. These approaches include sexual crossing, re-transformation, co-transformation and the use of linked transgenes. Novel, alternative 'enabling' technologies are also being developed that aim to use single transgenes to manipulate the expression of multiple genes. A chimeric transgene with linked partial gene sequences placed under the control of a single promoter can be used to co-ordinately suppress numerous plant endogenous genes. Constructs modelled on viral polyproteins can be used to simultaneously introduce multiple protein-coding genes into plant cells. In the course of our work on the lignin biosynthetic pathway, we have tested both conventional and novel methods for achieving co-ordinate suppression or over-expression of up to three plant lignin genes. In this article we review the literature concerning the manipulation of multiple genes in plants. We also report on our own experiences and results using different methods to perform directed manipulation of lignin biosynthesis in tobacco.

Selective inner hair cell loss in premature infants and cochlea pathological patterns from neonatal intensive care unit autopsies

BACKGROUND

Deafness and handicapping sensorineural hearing impairment occur frequently in neonatal intensive care unit survivors for unknown reasons.

PATIENTS AND METHODS

Hearing was tested early and repeatedly in neonatal intensive care unit patients with an auditory brainstem response (ABR) screener. The temporal bones of 15 nonsurvivors (30 ears) were fixed promptly (average, 5 hours) after death for histological evaluation.

RESULTS

Among these patients, 12 failed the ABR screen bilaterally, 1 passed unilaterally, and 2 passed bilaterally. Cochlear histopathologic conditions that could contribute to hearing loss included bilateral selective outer hair cell loss in 2 patients, bilateral selective inner hair cell loss in 3 (all premature), and a combination of both outer and inner hair cell loss in 2. Other hair cell abnormalities were noted; the 2 infants who had passed the ABR screen demonstrated normal histological features. Neuronal counts were normal.

CONCLUSIONS

Auditory brainstem response failure among these neonatal intensive care unit infants who died was extremely common in part owing to an unexpected histological alteration, selective inner hair cell loss among premature newborns, that should be detectable uniquely by the ABR testing method. Additional histological patterns suggest more than one cause for neonatal intensive care unit hearing loss. Hair cell loss patterns seem frequently compatible with in utero damage.

Dilated cardiomyopathy and sensorineural hearing loss: a heritable syndrome that maps to 6q23-24

BACKGROUND

Dilated cardiomyopathy (DCM) and sensorineural hearing loss (SNHL) are prevalent disorders that occur alone or as components of complex multisystem syndromes. Multiple genetic loci have been identified that, when mutated, cause DCM or SNHL. However, the isolated coinheritance of these phenotypes has not been previously recognized.

METHODS AND RESULTS

Clinical evaluations of 2 kindreds demonstrated autosomal-dominant transmission and age-related penetrance of both SNHL and DCM in the absence of other disorders. Moderate-to-severe hearing loss was evident by late adolescence, whereas ventricular dysfunction produced progressive congestive heart failure after the fourth decade. DNA samples from the larger kindred (29 individuals) were used to perform a genome-wide linkage study. Polymorphic loci on chromosome 6q23 to 24 were coinherited with the disease (maximum logarithm of odds score, 4.88 at locus D6S2411). The disease locus must lie within a 2.8 cM interval between loci D6S975 and D6S292, a location that overlaps an SNHL disease locus (DFNA10). However, DFNA10 does not cause cardiomyopathy. The epicardin gene, which encodes a transcription factor expressed in the myocardium and cochlea, was assessed as a candidate gene by nucleotide sequence analysis; no mutations were identified.

CONCLUSIONS

A syndrome of juvenile-onset SNHL and adult-onset DCM is caused by a mutation at 6q23 to 24 (locus designated CMD1J). Recognition of this cardioauditory disorder allows for the identification of young adults at risk for serious heart disease, thereby enabling early intervention. Definition of the molecular cause of this syndrome may provide new information about important cell physiology common to both the ear and heart.

Hereditary postlingual sensorineural hearing loss mapping to chromosome Xq21

BACKGROUND

Mutations on the X-chromosome clinically manifesting different phenotypes of hearing loss have been mapped to the long arm at different loci, DFN1-DFN3. Another defect in a family with sex-linked, postlingual, progressive sensorineural hearing loss was mapped to Xq.

METHODS

Clinically, the family was evaluated by physical and audiometric examination of 17 members including computerized tomographic (CT) evaluation of the proband. Molecular evaluation consisted of polymerase chain reaction amplification of patient genomic DNA and resolution 32P-labeled fragments by polyacrylamide gels. Inheritance of DNA alleles and deafness were analyzed using the MLINK computer program.

RESULTS

Five affected males demonstrated symmetrical sensorineural hearing loss as significant as 100 decibels (dB). Two carrier females had a milder loss with frequency findings of 10 dB to 60 dB. Computerized tomography (CT) evaluation of the temporal bones of the proband was normal. The odds were 200:1 that the responsible gene was linked to locus DXS986 (maximum lod score = 2.3 at 0 = 0). Analysis of recombination events defined by family members demonstrates that the responsible gene lies in a 21 cM (30 MB) interval, between loci DXS12175 and 1106. The disease locus in this family does not appear to map to DFN1 or DFN3.

CONCLUSION

The family described here, with affected males who have progressive, postlingual sensorineural hearing loss and mildly affected females maps most compatibly to the DFN2 locus. Analysis of hereditary deafness in this family refines the DFN2 locus to a 9.2 Mb region in chromosome X band q21 between DXS990 and DXS106.

Self-processing 2A-polyproteins--a system for co-ordinate expression of multiple proteins in transgenic plants

Achieving co-ordinate, high-level and stable expression of multiple transgenes in plants is currently difficult. Expression levels are notoriously variable and influenced by factors that act independently on transgenes at different genetic loci. Instability of expression due to loss, re-arrangement or silencing of transgenes may occur, and is exacerbated by increasing numbers of transgenic loci and repeated use of homologous sequences. Even linking two or more genes within a T-DNA does not necessarily result in co-ordinate expression. Linking proteins in a single open reading frame--a polyprotein--is a strategy for co-ordinate expression used by many viruses. After translation, polyproteins are processed into constituent polypeptides, usually by proteinases encoded within the polyprotein itself. However, in foot-and-mouth disease virus (FMDV), a sequence (2A) of just 16-20 amino acids appears to have the unique capability to mediate cleavage at its own C-terminus by an apparently enzyme-independent, novel type of reaction. This sequence can also mediate cleavage in a heterologous protein context in a range of eukaryotic expression systems. We have constructed a plasmid in which the 2A sequence is inserted between the reporter genes chloramphenicol acetyltransferase (CAT) and beta-glucuronidase (GUS), maintaining a single open reading frame. Here we report that expression of this construct in wheatgerm lysate and transgenic plants results in efficient cleavage of the polyprotein and co-ordinate expression of active CAT and GUS. Self-processing polyproteins using the FMDV 2A sequence could therefore provide a system for ensuring co-ordinated, stable expression of multiple introduced proteins in plant cells.

Brown-midrib maize (bm1)--a mutation affecting the cinnamyl alcohol dehydrogenase gene

Brown-midrib (bm) mutants of maize have modified lignin of reddish-brown colour. Although four independent bm loci are known, only one of the mutant genes has been previously identified. We report here that maize bm1, one of the less characterised mutants, shows severely reduced CAD activity in lignified tissues, resulting in the production of a modified lignin. Both the total lignin content and the structure of the polymer are altered by the mutation. We further describe the isolation and characterisation of the maize CAD cDNA and mapping of the CAD gene. CAD maps very closely to the known location of bm1 and co-segregates with the bm1 locus in two independent recombinant inbred populations. These data strongly support the premise that maize bm1 directly affects expression of the CAD gene.

Cloning and sequence analysis of laccase-encoding cDNA clones from tobacco

Three laccase-encoding cDNAs were cloned from a tobacco stem cDNA library. One of them contains a full length sequence coding for a cationic laccase. The predicted polypeptide sequence shows 48% identity with sycamore laccase. Amino acid comparisons with other laccases and ascorbate oxidases have shown that this new plant laccase sequence also contains four potential copper binding regions which are highly conserved among the blue copper oxidases.

A gene for non-syndromic autosomal dominant progressive postlingual sensorineural hearing loss maps to chromosome 14q12-13

We report a novel locus responsible for postlingual progressive sensorineural hearing loss (designated DFNA9) that maps to chromosome 14q12-13. A large kindred with autosomal dominant transmission of non-syndromic hearing loss was clinically studied. Hearing in affected individuals deteriorated at approximately 20 years of age and progressed to anacusis in the fifth decade. A random genome-wide search using polymorphic short tandem repeats demonstrated linkage with D14S121 (maximum two point LOD score = 6.19, theta = 0). Haplotype analysis of recombination events defined a 9 cM disease interval, between D14S252 and D14S49.

Vestibular neurectomy: retrosigmoid-intracanalicular versus retrolabyrinthine approach

Selective vestibular neurectomy is an effective treatment for intractable vertigo of peripheral vestibular origin when preservation of hearing is a goal. The retrolabyrinthine and retrosigmoid-intracanalicular approaches have been used predominantly at our institutions over the last 10 years. The results and complications of these two techniques were compared. No significant differences were found between hearing results in these two patient groups. The retrosigmoid-internal auditory can approach yielded better control of recurrent episodic vertigo, as well as superior ablation of postoperative ice-water caloric responses (p < 0.05). Surgical complications, including the incidence of cerebrospinal fluid leakage (greater in retrolabyrinthine approach) and postoperative headache (more prevalent in retrosigmoid approach), were also analyzed. To further evaluate the results of this study, data were reanalyzed and compared with previously published reports of selective vestibular nerve section.

The impact of dexamethasone on hearing loss in experimental pneumococcal meningitis

Bacterial meningitis, particularly that resulting from Streptococcus pneumoniae, is a common cause of acquired profound sensorineural deafness in children. The pathogenesis of meningogenic hearing loss has been investigated in an experimental rabbit model. In this study significant deafness was documented within the first 15 hours of infection. Initiation of antibiotic therapy at this time diminished the severity of hearing loss in most animals. The addition of dexamethasone to antibiotic therapy prevented the development of profound deafness. These results suggest this model will be useful in developing antiinflammatory strategies to improve the outcome of bacterial meningitis.

Low-frequency sensorineural loss: clinical evaluation and implications for hearing aid fitting

Spread of excitation in the cochlea places fundamental limits on the interpretation of audiometric pure-tone hearing loss as a simple map of dysfunction along the cochlear partition, and histologic evidence from human temporal bones will be presented to demonstrate the insensitivity of the audiogram to variations in pathology in the case of low-frequency hearing loss. This article will describe a clinical procedure using simultaneous pure-tone masking to improve upon the localization of cochlear disease, particularly for low-frequency hearing losses, and a model for using the Articulation Index (AI) to develop prognoses for hearing aid performance in these cases, which can then be tested. Fourteen patients with low-frequency hearing loss were divided into two groups based upon threshold shifts caused by a pure-tone masker: those that showed normal low-frequency threshold shifts and those that showed marked shifts at frequencies below the masker, indicating greater loss of function than shown by the unmasked audiogram. Hypothetical audiograms were then generated to model a complete loss of apical function for all patients. Measured speech recognition scores were then compared to AI predictions for the actual and hypothetical audiograms. Best agreement for the patients showing normal masking shifts was between the measured scores and the AI for the actual audiogram, whereas the best agreement for the patients showing marked shifts was with the AI for the hypothetical audiogram. The implications for hearing aid recommendation and fitting in these cases are discussed.

Progression of hearing loss in experimental pneumococcal meningitis: correlation with cerebrospinal fluid cytochemistry

The development of hearing loss and concomitant cerebrospinal fluid (CSF) cytochemical changes in a model of pneumococcal meningitis were examined. Rabbits were injected intracisternally with 10(5) pneumococci. Auditory evoked potentials to clicks and to 10- and 1-kHz tone bursts were recorded hourly; CSF was analyzed every 4 h. Sensorineural hearing loss developed in all animals beginning 12 h after infection and progressed to severe deafness. The onset of hearing loss was preceded by a CSF leukocytosis of > 2000 cells/microL and elevation of CSF protein and lactate concentrations to > or = 1 mg/mL. Temporal bone histopathology showed pneumococci and leukocytes extending from the CSF to the perilymph via the cochlear aqueduct. Hearing loss can develop early in the course of meningitis and is preceded by the abrupt onset of inflammatory changes in CSF. Progression of hearing loss is rapid and proceeds from cochlear base to apex in parallel with the degree of inflammation.

Identification and characterisation of cDNA clones encoding cinnamyl alcohol dehydrogenase from tobacco

Cinnamyl alcohol dehydrogenase (CAD, EC 1.1.1.195) is an enzyme involved in lignin biosynthesis. We have previously isolated pure CAD enzyme as two closely related polypeptides of 44 and 42.5 kDa from tobacco stems. In this paper, we report partial amino acid sequences of these two polypeptides. Based on the peptide sequences mixed oligonucleotides were used to screen a tobacco stem cDNA library and CAD cDNA clones encoding the two polypeptides were identified. DNA sequence comparisons indicate very high sequence identity between these clones both in the coding and in the 5' and 3' untranslated sequences. The close similarity between the two CAD genes leads us to suggest that they do not represent different isoforms but are the same gene from each of the two parental lines of Nicotiana tabacum cv. Samsun. Sequence comparisons with alcohol dehydrogenase 1 (ADH1) from yeast shows sequence similarities of ca. 30%, while comparisons with maize, barley and potato ADH1 sequences show similarities of not more than 23%.

The effect of cochlear hearing loss on auditory brain stem response latency

The effect of audiometric configuration on the auditory brain stem response was studied in a large patient sample, and wave I latencies, wave V latencies, and the I-V interwave intervals were compared to those from a previous report. Patients with notched hearing losses showed longer wave V latencies and I-V interwave intervals than those with other audiometric configurations, but the magnitude of the effect was relatively small, and the confidence limit for cochlear diagnosis was essentially the same as that based upon a cochlear hearing loss population without regard to audiometric configuration.

Purification and characterization of isoforms of cinnamyl alcohol dehydrogenase from Eucalyptus xylem

Two distinct isoforms of cinnamyl alcohol dehydrogenase, CAD 1 and CAD 2, have been purified to homogeneity from xylem-enriched fractions of Eucalyptus gunii Hook and partially characterized. They differ greatly in terms of both physical and biochemical properties, and can be separated by hydrophobic interaction chromatography on Phenyl Sepharose CL-4B. The native molecular weight of of CAD 1 is 38 kDa as determined by gel-filtration chromatography on Superose 6, and this isoform is likely to be a monomer since it yields a polypeptide of 35 kDa upon sodium dodecyl sulfatepolyacrylamide gel electrophoresis. It has a low substrate affinity for coniferyl and p-coumaryl alcohols and their corresponding aldehydes. No activity with sinapyl aldehyde and alcohol was detected. The more abundant isoform is CAD 2, which has a native molecular weight of 83 kDa and is a dinier composed of two subunits of slightly different molecular weights (42-43 kDa). These subunits show identical peptide patterns after digestion with N-chlorosuccinimide. The isoform, CAD 2, has a high substrate affinity for all the substrates tested. The two isoforms are immunologically distinct as polyclonal antibodies raised against CAD 2 do not cross-react with CAD 1. The characterization of two forms of CAD exhibiting such marked differences indicates their involvement in specific pathways of monolignol utilisation.

Purification and characterization of isoforms of cinnamyl alcohol dehydrogenase from Eucalyptus xylem

Two distinct isoforms of cinnamyl alcohol dehydrogenase, CAD 1 and CAD 2, have been purified to homogeneity from xylem-enriched fractions of Eucalyptus gunii Hook and partially characterized. They differ greatly in terms of both physical and biochemical properties, and can be separated by hydrophobic interaction chromatography on Phenyl Sepharose CL-4B. The native molecular weight of of CAD 1 is 38 kDa as determined by gel-filtration chromatography on Superose 6, and this isoform is likely to be a monomer since it yields a polypeptide of 35 kDa upon sodium dodecyl sulfatepolyacrylamide gel electrophoresis. It has a low substrate affinity for coniferyl and p-coumaryl alcohols and their corresponding aldehydes. No activity with sinapyl aldehyde and alcohol was detected. The more abundant isoform is CAD 2, which has a native molecular weight of 83 kDa and is a dinier composed of two subunits of slightly different molecular weights (42-43 kDa). These subunits show identical peptide patterns after digestion with N-chlorosuccinimide. The isoform, CAD 2, has a high substrate affinity for all the substrates tested. The two isoforms are immunologically distinct as polyclonal antibodies raised against CAD 2 do not cross-react with CAD 1. The characterization of two forms of CAD exhibiting such marked differences indicates their involvement in specific pathways of monolignol utilisation.

Purification and characterization of cinnamyl alcohol dehydrogenase from tobacco stems

Cinnamyl alcohol dehydrogenase (CAD) is an enzyme involved in lignin biosynthesis. In this paper, we report the purification of CAD to homogeneity from tobacco (Nicotiana tabacum) stems. The enzyme is low in abundance, comprising approximately 0.05% of total soluble cell protein. A simple and efficient purification procedure for CAD was developed. It employs three chromatography steps, including two affinity matrices, Blue Sepharose and 2'5' ADP-Sepharose. The purified enzyme has a specific cofactor requirement for NADP and has high affinity for coniferyl alcohol (K(m) = 12 micromolar) and coniferaldehyde (K(m) = 0.3 micromolar). Two different sized polypeptide subunits of 42.5 and 44 kilodaltons were identified and separated by reverse-phase HPLC. Peptide mapping and amino acid composition analysis of the polypeptides showed that they are closely related, although not identical.

Hearing loss and pneumococcal meningitis: an animal model

Clinical studies of predisposing factors in the development of hearing loss secondary to bacterial meningitis have produced conflicting results. An animal model of meningogenic labyrinthitis was developed for more precise study of these parameters. Rabbits were inoculated intrathecally with 10(5) pneumococci to induce meningitis. Hearing thresholds were measured using auditory-evoked responses to 1 kHz, 10 kHz, and click stimuli before infection and every 12 hours thereafter. Profound deafness occurred in all subjects at an average of 48 hours following infection. The incidence and severity of hearing loss was strongly correlated with the duration of meningitis. Temporal bone histology revealed acute inflammation of all perilymphatic spaces including the cochlear aqueduct. This model demonstrated that the risk and severity of hearing loss increase with the duration of meningitis and suggested that the cochlear aqueduct is an anatomic pathway for the extension of infection from the cerebrospinal fluid to the cochlea. The implications for therapy in humans is discussed.

The reaction specificities of the thylakoidal processing peptidase and Escherichia coli leader peptidase are identical

Proteins which are transported across the bacterial plasma membrane, endoplasmic reticulum and thylakoid membrane are usually synthesized as larger precursors containing amino-terminal targeting signals. Removal of the signals is carried out by specific, membrane-bound processing peptidases. In this report we show that the reaction specificities of these three peptidases are essentially identical. Precursors of two higher plant thylakoid lumen proteins are efficiently processed by purified Escherichia coli leader peptidase. Processing of one precursor, that of the 23 kd photosystem II protein, by both the thylakoidal and E. coli enzymes generates the correct mature amino terminus. Similarly, leader (signal) peptides of both eukaryotic and prokaryotic origin are cleaved by partially purified thylakoidal processing peptidase. No evidence of incorrect processing was obtained. Both leader peptidase and thylakoidal peptidase are inhibited by a synthetic leader peptide.

Different routes for integral protein insertion into Ricinus communis protein-body and glyoxysome membranes

Total polyadenylated RNA from ripening or germinating Ricinus communis L. endosperm was translated in rabbit reticulocyte lysate in the absence or presence of canine pancreatic microsomes. The products were immunoprecipitated using antibodies raised againts Triton X-114-extracted integral membrane proteins of protein bodies or glyoxysomes. While the proteins of proteinbody membranes were found to insert co-translationally into added microsomes, this was not observed in the case of glyoxysomal proteins. This observation was confirmed using antibodies raised against a purified glyoxysome membrane protein, alkaline lipase. These results indicate that different routes exist for the insertion of membrane proteins into the two organelles. In both cases membrane-protein insertion does not appear to be accompanied by proteolytic processing.

Experimental cryptosporidiosis in calves: clinical manifestations and pathological findings

Twenty-two calves between one and 20 days old were infected orally or by contact with cryptosporidia. Calves were maintained as either specific pathogen free, colostrum fed or sucking and were inoculated with either a bacteria free or a contaminated cryptosporidium preparation. Enteritis was characterised by depression, anorexia and diarrhoea and cryptosporidium oocysts were excreted during the clinical course of the illness. In the initial stages of the disease, cryptosporidium infestation was found throughout the small intestine; in the later stage the large intestine was also affected. Villous atrophy and fusion was present at small intestinal sites infected with cryptosporidia and lactase levels were depressed. No lesions were seen in infected large intestinal mucosa. Although the incubation period was longest (five to seven days) in calves infected by contact, there were few differences in the clinical course of disease or the pathological findings between any of the infected calves.

Intestinal changes associated with rotavirus and enterotoxigenic Escherichia coli infection in calves

Newborn calves inoculated with rotavirus, enterotoxigenic Escherichia coli (ETEC) serotype 020:K' x 106':K99:HNM, either alone or in combination, became depressed, anorectic, diarrhoeic and dehydrated. ETEC did not adhere to the intestine although there was extensive proliferation in the lumen. Only slight mucosal changes were induced by ETEC and the activity of membrane bound lactase remained normal. More severe mucosal damage and a decrease in lactase activity were found in newborn calves inoculated with either rotavirus or rotavirus and ETEC in combination. The most severe clinical illness was found in calves inoculated with both rotavirus and ETEC. Calves inoculated at 1 week of age with either rotavirus or ETEC remained clinically normal. Rotavirus infection produced slight mucosal changes and a reduction of lactase activity. In contrast, colostrum-fed or suckling calves up to 2 weeks old inoculated with both rotavirus and ETEC became clinically affected, showed severe mucosal damage and decreased lactase activity. There was no bacterial adhesion to the intestinal mucosa as observed by immunofluorescent labelling and light microscopy.

Enterocolitis in piglets caused by Cryptosporidium sp. purified from calf faeces

Twelve gnotobiotic piglets were dosed with a bacteria-free calf faecal homogenate which contained Cryptosporidium oocysts. The infection induced severe enterocolitis in piglets when inoculated at 1 day of age, moderate diarrhoea at 7 days of age and a subclinical infection at 15 days of age. In piglets aged 3 days or less, the entire intestine was extensively infected with Cryptosporidium and the mucosa was severely damaged. In piglets 7 days of age or older, the upper small intestine was sparsely infected with the organisms, but the ileum and the large bowel were heavily infected with associated mucosal damage.

Experimental colibacillosis in gnotobiotic piglets exposed to 3 enterotoxigenic serotypes

Three strains of enterotoxigenic Escherichia coli (ETEC) (064:KSNT, K88ac; 020:KSNT, K88ac and 08:K85ab, K99) originally cultured from outbreaks of diarrhoea in piglets a few hours old, were administered orally to gnotobiotic piglets. There was a marked age-related difference in the clinical response to infection between the 3 strains although they all produced heat-stable toxin. All 3 strains produced severe clinical signs of depression, anorexia, vomiting, diarrhoea, followed by dehydration and death in one-day-old piglets. In piglets infected at 3 days of age the two K88+ ETEC caused diarrhoea and death but the K99+ ETEC induced moderate diarrhoea only. In piglets infected at 7 days of age, the 064 strain produced severe diarrhoea and death, and 020 strain caused mild diarrhoea in 3 of 6 piglets with one death while the 08 strain caused no illness. Pathological changes in the intestinal tract associated with these infections were minimal, or absent. Immunofluorescent staining with homologous hyperimmune sera demonstrated adherence of the 3 ETEC strains to the brush border of small intestinal epithelial cells. Fluorescing organisms were observed in all infected piglets irrespective of the severity of clinical signs but the degree and extent of colonisation varied with the age of the piglets and the infecting strain. This may explain the difference in clinical response between the 3 strains.