Predictive value of microcirculation for pediatric extracorporeal membrane oxygenation weaning test: A monocentric prospective observational study

BACKGROUND

Extracorporeal membrane oxygenation (ECMO) is widely used for children treated for refractory respiratory failures or refractory cardiogenic shock. Its duration depends on organ functions recovery. Weaning is decided using macro-circulatory tools, but microcirculation is not well evaluated. Sidestream dark-field video imaging is used to assess the perfusion of the sublingual microvascular vessels. The aim of this study was to assess the predictive value of microcirculatory indices in ECMO weaning.

METHODS

This prospective monocentric study examined pediatric patients at Trousseau Hospital between March 2017 and December 2020. The study included all patients from 35 weeks of gestational age to 18 years old who were treated with ECMO. Children were divided into two groups: one with stability after weaning and the other with instability after weaning. We collected clinical and biological data, ventilation parameters, extracorporeal membrane oxygenation parameters, and drugs used at admission and after the weaning test. Microcirculations videos were taken after weaning trials with echocardiography and blood gas monitoring.

RESULTS

The study included 30 patients with a median age of 29 days (range: 1-770 days) at admission, including 18 patients who received venoarterial ECMO (60%). There were 19 children in the stability group and 11 in the instability group. Macrocirculatory and microcirculatory indices showed no differences between groups. The microvascular flow index was subnormal in both groups (2.3 (1.8-2.4) and 2.3 (2.3-2.6), respectively; p = 0.24). The microvascular indices were similar between cases of venovenous and venoarterial ECMO and between age groups.

CONCLUSION

Microcirculation monitoring at the weaning phase did not predict the failure of ECMO weaning.

Usefulness of implementation of a protective mechanical ventilation bundle during extracorporeal membrane oxygenation for pediatric acute respiratory distress syndrome

OBJECTIVE

Defining the best ventilatory settings under ECMO remains a challenging question. Despite a well-defined ARDS treatment before ECMO initiation, there is no recommendation on how to ventilate a patient under ECMO for P-ARDS. Only a few descriptive studies are available on ventilatory settings during respiratory ECMO. We aim at evaluating the usefulness of a protective ventilation bundle under ECMO and its capacity to reduce the ventilatory pressure in our ECMO center.

METHODS

We performed a monocentric retrospective study from January 2007 to December 2018. All children aged from 1 month to 18 years old and requiring an extracorporeal membrane oxygenation for a refractory acute respiratory distress syndrome were included. A protective mechanical ventilation under ECMO bundle has been developed in 2014. We compare the period 1 (before 2014) to the period 2 (after 2014).

RESULTS

Eighty-three patient had been included during the study. We reported a significant increase of PEEP and mean pressure respectively at day 3, day 7 and day 14 of ECMO during the period 2. Conversely, the driving pressure were significantly lower in the period 2 at day 3 (p: 0.009), day 7 (p:0.001) and day 14 (p: 0.001). We also shown a strong increase in the use of prone positioning during ECMO in the period 2 (p: 0.01). There was no significant effect of our bundle on the length of mechanical ventilation, of hospitalization and on the survival rate.

CONCLUSIONS

The implementation of a protective mechanical ventilation bundle during ECMO is usefulness to apply for lower ventilatory pressure and higher use of prone positioning. Nonetheless, the lack of power of our study prevents us from showing its efficacy on outcome criteria.

Unité mobile d’assistance circulatoire et respiratoire de l’enfant et du nouveau-né : une revue narrative

Les unités mobiles d’assistance circulatoire et respiratoire de l’enfant et du nouveau-né se sont développées au cours des dix dernières années. En effet, la mise en place d’une suppléance extracorporelle respiratoire ou circulatoire nécessite une équipe expérimentée et n’est pas disponible dans tous les centres hospitaliers pédiatriques. Or, les enfants atteints d’une défaillance circulatoire ou respiratoire réfractaire ne sont, pour la plupart, pas déplaçables vers une unité délivrant ce type de traitement de sauvetage. Les unités mobiles ont donc pour objectif de mettre à disposition ces technologies d’exception sur l’ensemble du territoire afin de garantir une égalité d’accès aux soins. Cependant, la haute technicité de ces thérapeutiques nécessite une équipe entraînée sachant poser et régler une assistance extracorporelle, prendre en charge un patient en défaillance respiratoire et/ou hémodynamique réfractaire et aguerrie à ces transports à haut risque. Le territoire français était jusqu’en 2014 très mal couvert par les unités mobiles pédiatriques et néonatales. Depuis, la création de plusieurs unités a permis une couverture totale du territoire. L’objectif de cette revue narrative sur les unités mobiles pédiatriques et néonatales est de résumer les différentes modalités de suppléance respiratoire et hémodynamique extracorporelle, d’en illustrer leurs différentes missions et leurs modalités de fonctionnement. Nous finirons par une description de leur efficacité en termes de survie et de survenue d’incidents en cours de transport.

Extracorporeal membrane oxygenation for immunocompromised children with acute respiratory distress syndrome: a French referral center cohort

BACKGROUND

Immunocompromised children are likely to develop a refractory acute respiratory distress syndrome (ARDS). The usefulness of providing extracorporeal life support (ECLS) to these patients is a subject of debate. The aim of our study was to report the outcomes and to compare factors associated with mortality between immunocompromised and non-immunocompromised children supported with veno-venous ECMO.

METHODS

We performed a retrospective monocentric study in the French pediatric ECMO center of Armand Trousseau Hospital, including all pediatric patients aged from 1 month to 18 years requiring ECLS for ARDS.

RESULTS

Between 2007 and 2018, one hundred and eleven (111) patients underwent ECMO for respiratory failure; among them twenty-five (25) were immunocompromised. Survival rate at 6 months after intensive care discharge was significantly lower for immunocompromised patients compared to non-immunocompromised ones (41.7% vs. 62.8%; p = 0.04). ARDS severity was similar between the 2 groups. Fungal pneumonias were reported only in immunocompromised patients (12.5% versus 0% in the control group; p = 0.001). Bleeding complications were significantly more frequent in the immunocompromised group and blood product transfusions were also more frequently required in this group.

CONCLUSIONS

Six months after intensive care discharge, survival rate of immunocompromised children supported with ECMO for pediatric ARDS is lower than for nonimmunocompromised patients. But, the expectation for a favorable outcome is real and it is worth it if their condition is likely to be compatible with a good long-term quality of life.

Acute myocarditis and multisystem inflammatory emerging disease following SARS-CoV-2 infection in critically ill children

BACKGROUND

A recent increase in children admitted with hypotensive shock and fever in the context of the COVID-19 outbreak requires an urgent characterization and assessment of the involvement of SARS-CoV-2 infection. This is a case series performed at 4 academic tertiary care centers in Paris of all the children admitted to the pediatric intensive care unit (PICU) with shock, fever and suspected SARS-CoV-2 infection between April 15th and April 27th, 2020.

RESULTS

20 critically ill children admitted for shock had an acute myocarditis (left ventricular ejection fraction, 35% (25-55); troponin, 269 ng/mL (31-4607)), and arterial hypotension with mainly vasoplegic clinical presentation. The first symptoms before PICU admission were intense abdominal pain and fever for 6 days (1-10). All children had highly elevated C-reactive protein (> 94 mg/L) and procalcitonin (> 1.6 ng/mL) without microbial cause. At least one feature of Kawasaki disease was found in all children (fever, n = 20, skin rash, n = 10; conjunctivitis, n = 6; cheilitis, n = 5; adenitis, n = 2), but none had the typical form. SARS-CoV-2 PCR and serology were positive for 10 and 15 children, respectively. One child had both negative SARS-CoV-2 PCR and serology, but had a typical SARS-CoV-2 chest tomography scan. All children but one needed an inotropic/vasoactive drug support (epinephrine, n = 12; milrinone, n = 10; dobutamine, n = 6, norepinephrine, n = 4) and 8 were intubated. All children received intravenous immunoglobulin (2 g per kilogram) with adjuvant corticosteroids (n = 2), IL 1 receptor antagonist (n = 1) or a monoclonal antibody against IL-6 receptor (n = 1). All children survived and were afebrile with a full left ventricular function recovery at PICU discharge.

CONCLUSIONS

Acute myocarditis with intense systemic inflammation and atypical Kawasaki disease is an emerging severe pediatric disease following SARS-CoV-2 infection. Early recognition of this disease is needed and referral to an expert center is recommended. A delayed and inappropriate host immunological response is suspected. While underlying mechanisms remain unclear, further investigations are required to target an optimal treatment.

Application of metrics constructed from vibrotactile thresholds to the assessment of tactile sensory changes in the hands

Two tools for assessing tactile sensory disturbances in the hands have been constructed from mechanoreceptor-specific vibrotactile threshold shifts, and thresholds changes with time, and employed in a prospective study of forest workers (N=18). Statistically significant positive threshold shifts (i.e., reductions in sensitivity compared to the hands of healthy persons) were found in five hands at study inception (13.9%), and 15 hands at follow-up (41.7%). Four patterns of threshold shift could be identified, involving selectively the median and/or ulnar nerve pathways and/or end organs. Statistically significant positive threshold changes (i.e., reductions in sensitivity with time) were recorded in 69.4% of the hands over a five-year period, even though a majority of the workers remained symptom free. If the thresholds recorded from subjects not working with power tools are used to control for aging, lifestyle, and environmental factors during the five year period, then 40% of the remaining subjects are found to be experiencing work-related threshold changes in their hands. The ability of the threshold shift metric to predict the numbness reported by these subjects shows that it is closely associated with the tactile sensory changes occurring in their hands.

Method for detecting small changes in vibrotactile perception threshold related to tactile acuity

Two metrics, expressing the change in mechanoreceptor-specific vibrotactile thresholds at a fingertip over a time interval of months or years, and the shift in threshold from the mean values recorded from the fingertips of healthy persons, have been constructed for thresholds measured from individual fingers. The metrics assume the applicability of the acute adaptation property of mechanoreceptors, which has been confirmed by thresholds obtained from 18 forest workers on two occasions, separated by 5 years. Hence, when expressed in decibels, both threshold changes and threshold shifts may be averaged at frequencies mediated by the same receptor population to improve precision. Differences between threshold changes at frequencies mediated by the same receptor population may be used to identify inconsistent subject performance, and hence potentially erroneous results. For this group of subjects, the threshold changes and threshold shifts at frequencies believed mediated by the slowly adapting type I (SAI) (4 and 6.3 Hz) and rapidly adapting type I (FAI) (20 and 32 Hz) receptors within each finger were correlated. In these circumstances, which may be expected to occur for some work-induced and systemic peripheral neuropathies, both threshold changes and threshold shifts may be summed over SAI and FAI receptors to improve precision, and hence the potential for interpretation.

The use of hearing protectors among forest, shipyard and paper mill workers in Finland--a longitudinal study

From 1953 to 1995 the usage rate of hearing protective devices (HPD) was tracked at a paper mill, a shipyard, and in selected areas of forestry work. For each work period, observations were made of HPD use among workers. In the paper mill, the usage rate increased steadily from 1965. In 1990, 39% of workers used HPDs full-time. At the shipyard, the usage rate remained low up to the mid-1980s, but thereafter the proportion of full-time users rose to 70%. A similar trend was noted in forest workers, with the full-time use at 97% by the 1990s. Due to the increased usage rate in all measured industries, the mean effective noise level at the ear has decreased to below 85 dB.

Effects of coldness on the protective performance of earmuffs

The type test of hearing protectors (HPD) for certification purposes will be conducted in laboratory at room temperature. Optionally, the mechanical durability of HPDs will be tested in cold environment by a drop test. The purpose of this study was to find out the relevance of the drop test, the change of performance in HPD protection, and finally to estimate the possible change of protection efficiency against noise in cold environment. In total, 22 HPDs were selected to the measurements: 18 earmuffs, and 4 earmuffs attached to an industrial helmet. Attenuation of each earmuff cup was measured by applying insertion loss method for the test subjects in cold. The change of attenuation and temperature of cushion ring was followed up to nine minutes using 30-second intervals for sampling. Three HPDs were damaged in the test. The replaceable cushion was broken in two earmuffs and in one helmet-mounted HPD. The replaceable parts were replaced, and the HPD with attachment failure was removed from insertion loss measurement. In nine HPDs the relative change was less than 3 dB, and was at worst 10 dB. This change was typically at low frequencies, 125 Hz at the beginning when cooled HPDs were placed. In various HPDs the time to get the attenuation levelled varied from 1.5 minutes to 8 minutes. The recovery was dependent on the temperature of the cushion ring. In all cases the temperature of the full attenuation was achieved when the cushion ring reached 7 degrees C. This temporary decrease in attenuation will have a minor effect to the protection efficiency, when the HPD is used full time during the whole exposure duration. A typical group of forest workers will have their exposure interrupted. The chain saws have to refuel, and the chain needs to be sharpened about every 40 minutes. During 6 hour daily operational time there will be about 9-10 minute break, long enough to cool the cushion ring back to below zero at -10 degrees C, if the helmet mounted earmuffs are placed in stand-by position. In the worst case this will cause 1.6 dB increase in daily exposure level to noise.

The effect of different noise types on the speech and non-speech elicited mismatch negativity

The effect of different types of real-life noise on the central auditory processing of speech and non-speech sounds was evaluated by the means of mismatch negativity and behavioral responses. Subjects (19-34 years old; 6 males, 4 females) were presented, in separate conditions, with either speech or non-speech stimuli of approximately equal complexity in five background conditions: babble noise, industrial noise, traffic noise, wide band noise, and silent condition. Whereas there were no effects of stimuli or noise on the behavioral responses, the MMN results revealed that speech and non-speech sounds are processed differently both in silent and noisy conditions. Speech processing was more affected than non-speech processing in all noise conditions. Moreover, different noise types had a differential effect on the pre-attentive discrimination, as reflected in MMN, on speech and non-speech sounds. Babble and industrial noises dramatically reduced the MMN amplitudes for both stimulus types, while traffic noise affected only speech stimuli.

Impulse noise and risk criteria

Impulse noise causes evidently more severe hearing loss than steady state noise. The additional effect of occupational impulse noise on hearing has been shown to be from 5 to 12 dB at 4 kHz audiometric frequency. Reported cases for compensated for hearing loss are prevalent in occupations where noise is impulsive. For impulse noise two measurement methods have been proposed: the peak level method and energy evaluation method. The applicability of the peak level method is difficult as even the recurrent impulses have different time and frequency characteristics. Various national risk criteria differ from international risk criteria. In France the maximum A-weighted peak level is 135 dB, and in the United Kingdom the C-weighted peak sound pressure is limited to 200 Pa (140 dB). This criterion of unweighted 200 Pa (140 dB) is used in European Union (EU) directive 86/188 and ISO 1999-1990 regardless of the number of impulses. The American Conference of Governmental Industrial Hygienists (ACGIH) has recommended that no exposure in excess of a C-weighted peak sound pressure level of 140 dB should be permitted. At work places these norms do not cause any practical consequences since the impulses seldom exceed 140 dB peak level. In several occupations the impulses are so rapid that they contribute only a minimal amount to the energy content of noise. These impulses can damage the inner ear even though they cause reduced awareness of the hazard of noise. Based to the present knowledge it is evident that there is the inadequacy of the equal energy principle in modelling the risk for hearing loss. The hearing protectors attenuate industrial impulse noise effectively due to the high frequency contents of impulses. Directive regarding the exposure of workers to the risks arising from noise requires that in risk assessment attention should be paid also to impulsive noise. So far there is no valid method to combine steady state and impulse noise. A statistical method for the measurements of industrial impulse noise is needed to get a preferably single number for risk assessment. There is an urgent task to develop risk assessment method and risk criteria for impulsive noise to meet the requirements of the upcoming European Union noise directive.

Age and noise-induced hearing loss

The purpose of the study was to evaluate the effect of noise, age and confounders in noise-induced hearing loss (NIHL). Information about work exposure, the use of hearing protective devices, audiogram, environmental and biological factors was collected from 406 paper mill workers exposed to noise levels of 91-94 dB(A), 124 forest workers exposed to noise levels of 96-99 dB(A) and 176 shipyard workers exposed to noise levels 95-97 dB(A). In addition to noise exposure, we collected the following confounders: smoking habits, serum cholesterol, systolic or diastolic blood pressure and use of analgesics. Subjects were classified based on median values, into high- and low-risk groups. The confounders were a significant source of hearing loss (HL) in younger and elderly groups of subjects, serum cholesterol level being the most important. In risk analysis the confounders partly masked the effects of noise in the development of HL. For subjects with less than two confounders, occupational noise exposure determined the development of NIHL. As the number of confounders increased, the noise exposure was overruled by these factors in the development of HL. In analysis where the subjects were matched with pairs by age, exposure, blood pressure and serum cholesterol level, the elderly subjects were more susceptible to NIHL than younger subjects. Factors independently but causally related to age were important in the development of NIHL among workers exposed to noise levels below 98 dB(A).

Autosomal dominant midfrequency hearing impairment

At present, 48 different gene loci have been localised and nine gene mutations have been characterised for non-syndromic hearing impairment. We have identified a large five-generation family with mid-and high-frequency hearing impairment. Family members were considered to be affected only if they had bilateral sensorineural hearing loss below the 90th percentile of an age and sex-dependent control audiometric curve of ISO class B. The inheritance of hearing impairment was autosomal dominant. Of seven affected individuals, six were females and one was male. The hearing loss among affected family members was bilateral, sensorineural and varies from mild to moderate. The type of audiogram was U-shaped. Genetic linkage studies are in progress and our preliminary data show exclusion in chromosome 6, chromosome 11 and chromosome 19 in already known loci for midfrequency hearing impairment. This means, we are mapping a novel locus for autosomal dominant midfrequency hearing impairment.

Effects of peak levels and number of impulses to hearing among forge hammering workers

The purpose of the study was to (1) compare measured and estimated hearing loss among forge hammering workers by applying models for risk assessment based on measurements of impulse noise, and (2) model the hazardous effects of impulse noise on hearing. Noise exposure and hearing loss among forge hammering workers were studied at two forge workshops of an automobile company, where the equivalent sound pressure levels (104 and 105 dB) were the same, but the peak levels and degree of impulsiveness were significantly different. The hearing threshold levels of selected groups of workers (97 and 235 workers) were determined. Comparison between the measured and expected hearing losses defined according to the ISO standard revealed 2 dB difference in excessive hearing loss (1 dB and 3 dB for the workers of workshop 1 and 2, respectively). The excessive hearing loss equals an increase of 3.5 years of exposure. The hearing loss of workers exposed to low impulsive noise could be predicted well using ISO 1999-1990. The hearing loss of workers exposed to high impulsive noise correlated significantly with the peak levels and the number of impulses in combination.

Hereditary hearing loss--the role of environmental factors

A large family with mid onset sensorineural hearing loss (HL) was used to study the effect of environmental factors on progression HL. Data from five-generations of one family were traced and 104 living members were included in the study. Audiograms were measured for 60 family members. We used an expert program to study the individual risk factors, which included the known risk factors for sensorineural HL. The pattern of inheritance in this HL family was autosomal dominant and 22 individuals were affected. The HL among affected individuals was symmetrical and varied from mild to severe. The mean age at onset of HL was 22 years. The mean deterioration of hearing at 2 kHz frequency was 1 dB/year. In the risk analysis the use of NSAID-analgetics and military noise exposure correlated with HL. There was no correlation between occupational and free time noise-exposure and HL. Analgetics may aggravate the HL in subjects with inherited HL. This type of genetic lesion is new and is not in those chromosomal areas already documented in the literature.

Sensorineural hearing loss after vibration: an animal model for evaluating prevention and treatment of inner ear hearing loss

Sensorineural hearing loss following a variety of acoustic trauma, including middle ear surgery, is well known. Current literature, which points to the deleterious influence of noise on the inner ear during surgery, has yet to assess the influence of vibration generated by the burr. The purpose of the study reported here was to establish an animal model that mimics drilling and can be used to explore methods of hearing loss prevention and treatment. A specially developed electromagnetic vibrator was calibrated and used in 59 guinea pigs to induce hearing loss. Both young and old guinea pigs were used. The bony external ear canal of guinea pigs were exposed to vibration or sound of varying duration and intensity. The vibration of the temporal bone and noise level in the middle ear were measured. Electrocochleography was recorded to evaluate the hearing loss. Among the young animals, 90% developed a significant threshold shift (TS > 20 dB), when vibrated with 250 Hz at an intensity of 6.2 m/s2 for 15 min. An average of 42 dB TS was observed. With 10 min exposure 63% showed a TS. The older animals vibrated for 5 min developed the same TS (mean TS 34 dB) as the young animals when vibrated for 10 min. The vibration-induced TS showed no recovery within 3 days of observation. In the contralateral ear 4 out of 5 animals showed TS > 20 dB. When exposed to sound levels exceeding the vibration-generated sound in the middle ear (119 dB at 250 Hz) only 2 out of II animals (18%) showed TS. The frequency of TS and level of TS were significantly greater in the vibrated animals than in sound-only exposed animals (p < 0.01). The degree of vibration-induced TS in the present animal model could be controlled by vibration intensity and duration. The older animals were more susceptible to vibration-induced inner-ear damage than younger animals. This model will be used in further studies to find methods for prevention and treatment of hearing loss during ear surgery.

Negative and translation termination-dependent positive control of FLI-1 protein synthesis by conserved overlapping 5' upstream open reading frames in Fli-1 mRNA

The proto-oncogene Fli-1 encodes a transcription factor of the ets family whose overexpression is associated with multiple virally induced leukemias in mouse, inhibits murine and avian erythroid cell differentiation, and induces drastic perturbations of early development in Xenopus. This study demonstrates the surprisingly sophisticated regulation of Fli-1 mRNA translation. We establish that two FLI-1 protein isoforms (of 51 and 48 kDa) detected by Western blotting in vivo are synthesized by alternative translation initiation through the use of two highly conserved in-frame initiation codons, AUG +1 and AUG +100. Furthermore, we show that the synthesis of these two FLI-1 isoforms is regulated by two short overlapping 5' upstream open reading frames (uORF) beginning at two highly conserved upstream initiation codons, AUG -41 and GUG -37, and terminating at two highly conserved stop codons, UGA +35 and UAA +15. The mutational analysis of these two 5' uORF revealed that each of them negatively regulates FLI-1 protein synthesis by precluding cap-dependent scanning to the 48- and 51-kDa AUG codons. Simultaneously, the translation termination of the two 5' uORF appears to enhance 48-kDa protein synthesis, by allowing downstream reinitiation at the 48-kDa AUG codon, and 51-kDa protein synthesis, by allowing scanning ribosomes to pile up and consequently allowing upstream initiation at the 51-kDa AUG codon. To our knowledge, this is the first example of a cellular mRNA displaying overlapping 5' uORF whose translation termination appears to be involved in the positive control of translation initiation at both downstream and upstream initiation codons.

Smoking as a risk factor in sensory neural hearing loss among workers exposed to occupational noise

The effect of smoking on hearing was investigated among 199 professional forest workers and 171 shipyard workers. The effect of age on hearing was corrected with Robinson's model for an audiologically screened population. The exposure of the subjects to noise and their history of tobacco smoking were examined, with special reference to blood pressure and occupational Raynaud's phenomenon. Smoking without the presence of any other risk factors did not increase the risk for sensory neural hearing loss, but smoking in combination with elevated blood pressure and occupational Raynaud's phenomenon put workers at higher risk for hearing loss than any of these factors alone.

Unexpected and coordinated expression of Spi-1, Fli-1, and megakaryocytic genes in four Epo-dependent cell lines established from transgenic mice displaying erythroid-specific expression of a thermosensitive SV40 T antigen

Most erythroleukemic cell lines established in vitro coexpress erythrocytic and megakaryocytic markers that often are associated with expression of Spi-1 and/or Fli-1 transcription factors known as transactivators of megakaryocyte-specific promoters. In the present study, we examined the possibility of establishing new cell lines keeping strictly erythroid-specific properties in vitro through the targeted and conditional immortalization of erythrocytic progenitors. For that purpose, we established several lines of transgenic mice displaying erythroid-specific expression of a thermosensitive SV40 T antigen. As expected, these transgenic mice developed splenomegaly due to the massive amplification of Ter 119 positive erythroid nucleated cells expressing T antigen. Despite this drastic effect in vivo, the in vitro immortalization of erythropoietin-dependent erythroid progenitors unexpectedly occurred at low frequency, and all four cell lines established expressed both erythrocytic (globins) and megakaryocytic markers (glycoprotein IIb, platelet factor 4) as well as Spi-1 and Fli-1 transcripts at permissive temperature. Switching the cells to the nonpermissive temperature led to a marked increase in globin gene expression and concomitant decrease in expression of Spi-1, Fli-1, and megakaryocytic genes in an erythropoietin-dependent manner. Interestingly, enhanced expression of Spi-1 and Fli-1 genes already was detected in the Ter 119 positive cell population of transgenic mice spleen in vivo. However, like normal Ter 119 erythroid cells, these Ter 119 positive cells from transgenic mice still expressed high levels of beta-globin and very low or undetectable glycoprotein IIb and platelet factor 4 megakaryocytic transcripts. Taken together, these data indicate that the unexpected expression of megakaryocytic genes is a specific property of immortalized cells that cannot be explained only by enhanced expression of Spi-1 and/or Fli-1 genes.

Spi-1/PU.1 is a positive regulator of the Fli-1 gene involved in inhibition of erythroid differentiation in friend erythroleukemic cell lines

Spi-1/PU.1 and Fli-1 are two members of the ETS family of transcription factors whose expression is deregulated by proviral insertion in most erythroleukemic cell lines induced by the spleen focus-forming virus (SFFV) and Friend murine leukemia virus (F-MuLV) components of the Friend viral complex, respectively. In this study, we present evidence that transcription of the Fli-1 gene is positively regulated by Spi-1/PU.1 in SFFV-transformed cell lines: (i) all SFFV-transformed cell lines expressing Spi-1/PU.1 are characterized by a specific pattern of Fli-1 gene transcripts initiated in the -200 region instead of position -400 as reported for F-MuLV-transformed cell lines; (ii) these Fli-1 transcripts initiated in the -200 region are downregulated in parallel with that of Spi-1/PU.1 during hexamethylenebisacetamide (HMBA) induced differentiation; and (iii) Fli-1 transcription is upregulated in SFFV cells lines following stable transfection of a Spi-1/PU.1 expression vector. Furthermore, we found by transient transfection assays that the -270/-41 region of the Fli-1 gene displays promoter activity which is transactivated by Spi-1/PU.1. This promoter is strictly dependent on the integrity of two highly conserved ETS DNA binding sites that bind the Spi-1/PU.1 protein in vitro. Finally, we show that transfection of constitutive or inducible Fli-1 expression vectors in SFFV-transformed cells inhibits their erythroid differentiation induced by HMBA. Overall, these data indicate that Fli-1 is a target gene of the Spi-1/PU.1 transcription factor in SFFV-transformed cell lines. We further suggest that deregulated synthesis of Fli-1 may trigger a common mechanism contributing to erythroleukemia induced by either SFFV or F-MuLV.

Coactivation of human alpha1- and alpha2-globin genes in single induced MEL cells containing one human alpha-globin locus

We developed a reverse-transcription polymerase chain reaction assay, performed on single isolated cells, to demonstrate the coexpression of human alpha1- and alpha2-globin mRNA in induced mouse erythroleukemic cells containing a single human alpha-globin locus. These results indicate that both alpha1 and alpha2 genes are activated from the same alpha-globin gene locus implying that HS-40-dependent transcriptional activation is mediated, either by a simultaneous interaction of HS-40 with both a alpha1 and alpha2-globin gene promoters, or by a dynamic process characterized by alternative, but short-lived, interactions with each alpha-globin gene promoter.

Postural stability, neck proprioception and tension neck

We examined whether tension neck (TN) may due to inadequate proprioceptive and vestibular activation of the cervico-collic reflex (CCR). CCR and vestibulospinal responses (VSRs) were recorded from 106 forest workers by stimulating the neck, lumbar or calf proprioceptors by vibration. The VSRs were recorded with posturography. TN occurred in 27 out of 106 subjects. The subjects with TN (48.5 years) were older than those without TN (43.1). The mean body sway during quiet stance was the same in both groups during the neck stimulation. In subjects with tension neck stimulation of neck or lumbar proprioceptors caused excessive, unpredictable body excursion in the lateral and anteroposterior direction that continued after stimulation. Results from stimulation of lower limb proprioceptors did not significantly differ between the 2 groups. In logistic regression analysis a model to predict TN consisting of perstimulatory postural stability (odds ratio 1.4) and poststimulatory postural stability (odds ratio 1.8) turned out to be statistically significant. The anatomical findings of CCR in the medulla oblongata suggest that neck muscle afferents control the posture and muscle activity of the neck. The erroneus facilitation of proprioception in TN subjects indicate that TN may be raised by inadequate facilitation of CCR.

The noise level in magnetic stimulation

The noise generated by stimulating coils may jeopardize the hearing of the patients as well as the hearing of the examiner. To evaluate the potential risk caused by the impulse noise of stimulating coils, we examined the A-weighted peak sound pressure levels from five different types of magnetic stimulator coils. At a distance of 10 cm, with 100% stimulation intensity, the coils with Dantec and Magstim stimulators created maximum peak sound pressure levels of 110 dB. Correspondingly, Cadwell MES-10 created maximum peak sound pressure levels of 132 dB. The decrease in the peak levels followed the distance rule quite closely. At a distance of 40 cm, the decrease in peak level was on average 14 dB (range -1-(+)1 dB). Based on American Conference of Governmental Industrial Hygienists (ACGIH) threshold limits of impact noise, the permitted maximum daily number of magnetic stimuli would be 1000 to 10,000. The permitted number of daily stimuli may be difficult to exceed in clinical practice. We consider the risk as small for the patients that are being examined and the operator using magnetic stimulation. The potential risk can be further diminished by even very light weighted hearing protectors providing proper attenuation to the coil impulses.

Postural control in Menière's disease and acoustic neurinoma when studied on a linearly oscillating platform

We investigated the effect of visual control on postural stability on a moving platform in 36 patients with Menière's disease (MD) in 25 patients with operated acoustic neurinoma (AN) and in 19 healthy controls. The force platform was placed on rails and oscillated linearly at frequencies from 0.2 to 5 Hz at a constant velocity of 30 mm/s. In all subjects, the support surface oscillation produced postural instability that differed significantly from the base line stability. The body sway velocity increased almost linearly with the increase of stimulation frequency. The MD patients swayed more than the AN patients at base line measurements in non-visual conditions but not during platform movement. In visual conditions the AN patients stabilized their posture significantly better than the MD patients, who showed deteriorating visual control of posture during platform movement. The controls differed from the patients in all test conditions except 5 Hz stimulation, which causes the body segment to fall into resonance. The Romberg quotients (RQ) in MD patients was significantly poorer during platform movement than in controls, except at 5 Hz stimulation. The AN patients had higher RQ values than controls, and mainly used vision to compensate their vestibular deficit. Thus, patients with MD fail to control their posture efficiently with vision during movement which may explain the visually induced dizziness in MD patients.

Vestibular evoked responses in man: methodological aspects

We have developed a stimulation method where the subject is sitting and the head is rotated with shock bursts elicited by a shaker with a repetition rate of 2 Hz. The head movement is monitored with an accelerometer mounted on the cheek by a head band. The maximum amplitude of the head movement is 3 degrees. The electrodes were places on vertex with a negative electrode on the mastoid. During stimulation, 90 dB white noise was applied to the ears to mask the noise generated by the stimulus. We recorded following responses: i) VER from ipsilateral ear, ii) VER from contralateral ear, iii) eye movement with EOG, and iv) movement of the head. Amplification and averaging of the signal were made with an evoked response recorder (Nihon Kohden, Neuropac four). From 200 to 2,000 averaged responses were collected and stored for further analysis on a floppy disc. During second stage filtering the data were fed into a microcomputer where appropriate programs were used to eliminate the EMG and movement artifacts.

Structural characterization of the beta-globin gene cluster in an individual expressing a very low level of G gamma globin chains

We report the case of a normal individual displaying an extremely unbalanced G gamma/A gamma-globin ratio (G gamma-globin chains undetectable by urea/triton/ acrylamide gel electrophoresis and just reaching the threshold of detection by high performance liquid chromatography) associated with a very low level of G gamma-globin mRNA (at the most 5% of total gamma-mRNA after reverse transcriptase polymerase chain reaction determination). By DNA Southern blotting and sequencing, the very low level of G gamma-globin chains in this individual was found in association with subhaplotype [+ -----] (Hinc II 5' to epsilon, Xmn I 5' to G gamma, Hind III in G gamma and A gamma, Hinc II in and 3' to psi beta), with G gamma- and A gamma-globin gene sequences of the B type chromosome, and with a number of AT repeats in the locus control region hypersensitive site-2 site, similar to that reported to be associated with the Bantu beta S haplotype. These structural characteristics, described for the first time combined in the same individual, suggest that the G gamma/A gamma ratio in adults, is controlled by sequences distributed all along the beta-globin gene cluster.

Developmental regulation of human gamma- and beta-globin genes in the absence of the locus control region

Two lines of transgenic mice carrying a normal 40-kb Kpn I beta-globin cluster transgene lacking the locus control region (LCR) were analyzed for the expression of human gamma- and beta-globin genes during mouse development. After RNase protection assays, the ratios of human G gamma-, A gamma-, or beta-mRNAs relative to endogenous mouse zeta + alpha mRNAs were obtained for each stage of development. The two gamma transgenes were expressed in day-11.5 blood (embryonic stage) and day-13.5 blood (early fetal stage), but their expression was markedly decreased by day 16.5 of fetal life. Expression of the beta transgene was essentially absent at day 13.5, appeared at a low level by day 16.5, and was maximal by day 18.5, reaching a level similar to that observed in adult mice. Therefore, developmentally regulated expression of the human gamma- and beta-globin transgenes was obtained in the absence of the LCR. The relative expression of human gamma- and beta-globin genes was also examined in mice carrying 40-kb Kpn I beta-cluster transgenes with two different base substitutions associated with nondeletion forms of hereditary persistence of fetal hemoglobin (HPFH), -202 C-->G G gamma HPFH and -117 G-->A A gamma HPFH. The ratio of G gamma- to beta-globin transcripts was markedly increased in red blood cells of adult mice from three different lines carrying the transgene with the -202 G gamma HPFH mutation. This result confirms our previous preliminary results (Tanaka et al: Ann NY Acad Sci, 612:167, 1990) indicating that the -202 G gamma HPFH phenotype was reproduced in transgenic mice. The relatively low levels of G gamma-mRNA expression in adult mice carrying the non-HPFH transgene excludes a major influence of the 3' beta-globin enhancer, present upstream of the G gamma gene because of the tandem repeat insertion, as a factor in the persistent G gamma gene expression observed in blood of adult mice carrying the -202 G gamma HPFH transgene. This conclusion is also supported by the fact that, in mice carrying the -117 A gamma HPFH transgene, G gamma-globin mRNA was detected in blood of adult animals only at low levels similar to that observed in the non-HPFH lines. However, the A gamma-HPFH phenotype was not reproduced in the transgenic lines carrying the -117A gamma HPFH mice.

Effect of hand-arm vibration on inner ear and cardiac functions in man

To evaluate distant effects of hand-arm vibration we studied Finnish forestry workers using chain saw during the years 1972 through 1990. The hearing was tested annually and individual regression curves for sensorineural hearing loss (SHL) were calculated. Robinson's model was used in prediction of SHL. The heart rate variation (HRV) indexes at rest and during deep breathing test were analyzed to measure autonomic nervous function. In Robinson's model the measured SHL (17.8 dB) respected the predicted SHL (17.2 dB). The subjects with VWF had on average, 10 dB greater hearing loss than those who did not have VWF. The regression model based increase of hearing loss during follow up correlated with ageing, not to VWF. The intercept differed significantly in those with VWF from those without VWF. We found a significant difference between HRV indexes during deep breathing test in those with the shortest and those with the longest vibration exposure. The HRV decreased with age, but multiple regression analysis showed that the total exposure time to vibration had an independent negative association with HRV indexes. Our results suggest that prolonged exposure to vibration caused by chain saw has negative effects an autonomic functions. The aggravated hearing loss in subjects with VWF may be due to vibration induced changes in the autonomic nervous system or internal factors of the blood vessels.

Vibration exposure and prevention in Finland

The number of annually compensated occupational diseases due to exposure to hand-arm vibration (HAV) has decreased during the last 15 years. The number of exposed workers has been declining in Finland, especially in forestry work, as harvesters have increasingly replaced manual chain saw operations. During the entire 1970s, forest work caused more cases of vibration-induced occupational diseases than all industrial branches together. The decrease is mainly due to the technical development of chain saws, but also to the effective health care services in Finland. Other factors such as warm transport, warm rest cabins in which to take pauses at work, warm meals, adequate protective clothing, and vocationally adjusted early medical rehabilitation have helped to cut down health hazards, especially in forest work. The number of new cases has been decreasing in Finland not only in forestry but also in other industries. In Finland a considerable amount of research has been conducted to hand-arm vibration, resulting in the increased awareness of the health risks related to certain occupations. This has helped to carry out the Primary Health Care Act (1972) followed by the Occupational Health Care Act (1979) which obligates employers to arrange occupational health care for their employees. We believe that the research activity has contributed significantly to achieving the present health in Finnish work places. The purpose of the present paper is to describe the cases of occupational exposure to HAV, and the effectiveness of different preventive measures in Finland.

Smoking habits and postural stability

PURPOSE

It has been reported that tobacco smoking temporarily affects postural stability We have examined whether smoking habits have a long-term effect on the body balance control using computer-aided posturography.

SUBJECTS AND METHODS

The postural stability of 80 male forest workers was measured with a force platform technique with eyes closed. Average body sway velocity (ASV [mm/s]) was determined and used as a stability index. Detailed interviews on tobacco smoking and otologic examinations were carried out. Smoking habits were classified into five categories: nonsmokers (53.8%), ex-smokers (17.5%) and current smokers, comprising light (3.8%), moderate (15%), and heavy (10%) smokers.

RESULTS

The smoking habits of the subjects correlated significantly with ASV, but hours of the exposure to noise and hand-arm vibration from chain saws did not. The correlation of the smoking habits remained significant even after eliminating the effect of age and exposure by partialization. Age in itself had no effect on ASV but interacted with smoking to increase ASV. The group means of ASV increased with the increase in smoking. Significant differences in ASV were found in the moderate and heavy smokers compared with the nonsmokers.

CONCLUSION

Smokers exhibited more unstable posturographic results than nonsmokers. Smoking habits were suggested to have a long-term effect on the posture control system.

Hearing loss risk from exposure to shooting impulses in workers exposed to occupational noise

The effect of shooting impulses on hearing was analysed in 150 professional forest workers exposed to noise from chain saws. The exposure to shooting impulses (Lesi) was designed to take into account the peak levels of shooting impulses, their number and use of hearing protectors. Hearing loss was dependent on Lesi even after allowing for the age of subjects and their exposure to chain saw noise. Hearing threshold levels were compared between pairwise matched groups with high and low Lesi. Proper matching was achieved for age, chain saw noise, salicylate consumption, blood pressure, cholesterol, smoking and vibration-induced white finger symptoms. The workers with high Lesi had 9 dB greater hearing loss at 4 kHz and 10 dB greater hearing loss at 8 kHz than those with low Lesi, the difference being significant at P < 0.05 level. In evaluation of noise-induced hearing loss the exposure to shooting impulses from different calibre weapons should be determined since they increase the extent of hearing loss. The present study describes the Lesi method which more accurately evaluates the harmful effects of shooting noise impulses on hearing.

Postural stabilization on a moving platform oscillating at high frequencies

The effect of a fore-aft oscillating platform on postural stability was studied in nine healthy volunteers. The force platform technique was used with automatic analysis that evaluated the position of the center point of force as a function of time. The duration of stimulation lasted 90 s and the perturbation frequencies ranged from 8 to 24 Hz, and were given at constant rms acceleration of 4 m/s2. When compared with a vibration-free baseline stance, horizontal vibration of the platform caused significantly worse postural stability in all subjects. Test frequencies of 8 and 10 Hz produced greater sway velocities than perturbation at frequencies of 14 and 16 Hz. The results indicate that horizontal perturbation of the support surface leads to postural instability that is frequency-dependent.

Postural control and age

We quantified the effect of vision, pressoreceptor function and proprioception on the postural stability at different ages. Altogether 212 healthy volunteers (ages from 6 to 90 years) were examined by using a computerised force platform. The sway velocity (SV) was measured with eyes open and eyes closed during quiet stance on a bare platform and a foam plastic covered surface. In addition, to study the proprioceptive system, pseudorandom vibration perturbation was applied on the calf muscles. The SV showed a U-shaped curve: the children and the oldest swayed most. Equilibrium was most stable around 50 years. The visual system was of most importance for balance control in the old. The children were sensitive of pressoreceptor and proprioceptive perturbation, indicating the importance of these systems for their postural control.

Vibration syndrome among Finnish forest workers between 1972 and 1990

A longitudinal study on vibration syndrome among professional forest workers was carried out in Finland from 1972 to 1990. In the course of the follow-up the weighted vibration acceleration of chain saws decreased from about 14 to 2 m/s2. The prevalence of vibration-induced white finger (VWF) decreased gradually from 40% to 5%. Numbness occurred mainly at night, and its prevalence decreased from 78% to 28%. During part of the follow-up period (1975-1990) the complaints of hand muscle weakness decreased from 19% to 9%. Disorders of the musculoskeletal system were considered to cause more disability than VWF. The decreased vibration acceleration and the lighter weight of chain saws were considered the main reasons for the decrease in the prevalence of vibration-induced symptoms.

In vivo measurements of lead in bone at four anatomical sites: long term occupational and consequent endogenous exposure

Measurements of bone lead concentrations in the tibia, wrist, sternum, and calcaneus were performed in vivo by x ray fluorescence on active and retired lead workers from two acid battery factories, office personnel in the two factories under study, and control subjects. Altogether 171 persons were included. Lead concentrations in the tibia and ulna (representative of cortical bone) appeared to behave similarly with respect to time but the ulnar measurement was much less precise. In an analogous fashion, lead in the calcaneus and sternum (representative of trabecular bone) behaved in the same way, but sternal measurement was less precise. Groups occupationally exposed to lead were well separated from the office workers and the controls on the basis of calculated skeletal lead burdens, whereas the differences in blood lead concentrations were not as great, suggesting that the use of concentrations of lead in blood might seriously underestimate lead body burden. The exposures encountered in the study were modest, however. The mean blood lead value among active lead workers was 1.45 mumol l-1 and the mean tibial lead concentration 21.1 micrograms (g bone mineral)-1. The kinetics of lead in the tibia appeared to be noticeably different from that in the calcaneus. Tibial lead concentration increased consistently both as a function of intensity of exposure and of duration of exposure. Calcaneal lead concentration, by contrast, was strongly dependent on the intensity rather than duration of exposure. This indicated that the biological half life of lead in calcaneus was less than the seven to eight year periods into which the duration of exposure was split. Findings for retired workers clearly showed that endogenous exposure to lead arising from skeletal burdens accumulated over a working lifetime can easily produce the dominant contribution to systemic lead concentrations once occupational exposure has ceased.

Relevance of the Tullio phenomenon in assessing perilymphatic leak in vertiginous patients

The Tullio phenomenon was studied in 57 control subjects, in 7 patients with confirmed PLF and in 149 patients with different types of inner ear pathology. The subjects were exposed to low-frequency sound (LFS) with sound pressure levels ranging from 130 to 132 dB and at frequencies of 25, 50, and 63 Hz. The duration of each stimulation was 30 seconds. The postural responses were measured using a force platform and analyzed with a computer. In control subjects the LFS stimulation somewhat improved the postural stability. All patients with PLF showed significantly altered postural stability during LFS exposure. Also about 20 percent of patients with labyrinthine vertigo, patients with Menièré's disease, patients with chronic middle ear disease (with vertigo) had pathologic response to LFS. None of the patients with pure sensorineural hearing loss without vertigo responded to LFS. Post-urography with LFS loading is a new, promising tool in detection of PLF, but the specificity of the test is still unsatisfactory.

Tullio phenomenon and postural stability: experimental study in normal subjects and patients with vertigo

The effect of low-frequency sound (LFS) on postural stability was studied in 55 healthy volunteers and in 152 patients with vertigo due to different types of inner ear disease. The sound pressure levels ranged from 130 to 132 dB and were given at frequencies of 25, 50, and 63 Hz. The duration of each stimulation lasted 30 seconds. The postural responses were measured with a force platform. The LFS stimulation improved the postural stability of the healthy subjects through the alerting response. We did not observe any difference in the body sway according to whether the LFS was delivered with monaural or binaural stimulation. Twenty-six percent of the patients with Meniere's disease, 40% with chronic otitis media with vertigo, and 26% with vertigo of peripheral origin experienced significant postural instability at least at two of the three test frequencies during stimulation with LFS. The results demonstrate that in subjects with different types of inner ear disease the vestibular system starts to respond to LFS. The activation of vestibulospinal responses by LFS seems to be an expression of the Tullio phenomenon.

Postural stability on moving platform oscillating at high frequencies. Effect of vestibular lesion

The effect of linear perturbation at a frequency range of 8 to 24 Hz on postural stability was studied in 7 patients with unilateral vestibular function loss. Force platform technique was used with automatic analysis resulting in the sway velocity of the center point of force. In all patients the support surface movement produced increased sway velocity which was significantly greater than in the controls. Tests at lower frequencies (8 and 10 Hz) produced higher sway velocities than tests at higher frequencies (12, 14, 16 and 24 Hz). The results indicate that the vestibular system controls postural reflexes at a substantially higher frequency range than hitherto suggested.

Repeatability and effect of instruction of body sway

The effect of instruction and repeatability of posturography measurement was studied in 24 healthy volunteers. In an instruction, "stable" (inverted pendular model) and "relaxed" (segmental oscillating model) positions were studied. In addition, the effect of habituation adaptation, and day-to-day variation were investigated. Sway velocity and average and maximum displacement during vibration perturbated stance were analysed. In individual responses, no statistically significant day-to-day variation could be observed and the individual variation was small. In the "relaxed" condition, the instability was greater when maximum displacement was analysed. No significant changes in sway velocity and average displacement were observed. The results demonstrated remarkable stability of normal postural control mechanism.

The Tullio phenomenon in patients with Menière's disease as revealed with posturography

The effect of low frequency sound (LFS) on postural stability was studied in 55 healthy volunteers and in 50 patients with Menière's disease. The sound levels ranged from 130 to 132 dB and were given at frequencies of 25, 50 and 63 Hz. The patients with Menière's disease displayed increased body sway during stimulation. In the individual response, 26% of the patients with Menière's disease experienced significant body sway. The results demonstrate that subjects with Menière's disease are sensitive to low frequency sound. The activation of vestibulo-spinal responses by low frequency sound seems to be a result of the Tullio phenomenon, in which sound energy activates the vestibular end-organ.

Vibration perception threshold of forest worker's finger during temporary obstructed blood circulation

Vibration detection threshold (VPT) of 149 professional forest workers was measured during a compulsory annual health examination. The authors' earlier developed measuring method for VPT of finger was modified. The blood circulation of the hand was obstructed for 6 min and VPT was measured 4 min after releasing the obstruction. VPTs of all forest workers increased during obstruction. In forest workers suffering from decreased hand grip force (decreased HGF) the increase of VPT differed significantly from forest workers without symptoms, and VPT in the former group still increased after releasing the obstruction. VPT remained also at the raised level after releasing the obstruction with forest workers suffering from vibration-induced white finger (VWF). Nevertheless, on an individual basis even the modified measuring method failed to discriminate subjects without symptoms from those with symptoms of hand-arm vibration syndrome. The raised VPT and sensitivity for obstruction of blood circulation suggest that the reason for decreased HGF in forest workers may be a consequence of an injury in the peripheral nerves.

Two elliptocytogenic alpha I/74 variants of the spectrin alpha I domain. Spectrin Culoz (GGT----GTT; alpha I 40 Gly----Val) and spectrin Lyon (CTT----TTT; alpha I 43 Leu---Phe)

Spectrin alpha I/74 elliptocytosis results from abnormalities involving the "head" region of spectrin dimer. Increased susceptibility to trypsin enhances cleavage of the alpha spectrin chain, yielding an increased amount of the alpha I 74-kD fragment at the expense of the alpha I 80-kD parent fragment. Recently we showed that the mutations causing the Sp alpha I/74 abnormality may lie in the alpha- or the beta-chain, and that spectrin Culoz and spectrin Lyon were two (alpha I/74) alpha-variants, respectively. We now show that the spectrin Culoz alpha I domain undergoes prominent tryptic cleavage after Lys 42, whereas cleavage prevails after Arg 39 in spectrin Lyon. Applying the polymerase chain reaction (PCR) technique to exon 2 of the spectrin alpha I domain, we have established that the mutation responsible for spectrin Culoz is alpha I 40 Gly----Val; GGT----GTT. Applying the PCR technique to the cDNA derived from reticulocyte mRNA, we have shown that the mutation responsible for spectrin Lyon is alpha I 43 Leu----Phe; CTT----TTT. Studies of normal controls and of family members using dot blot hybridization with allele-specific oligonucleotide probes confirmed these results. Variants such as spectrin Culoz and spectrin Lyon should provide insight into a region that participates in spectrin dimer self-association and whose susceptibility to proteolysis must reflect subtle conformational changes.