Contractile behavior of the gastrocnemius medialis muscle during running in simulated hypogravity

Vigorous exercise countermeasures in microgravity can largely attenuate muscular degeneration, albeit the extent of applied loading is key for the extent of muscle wasting. Running on the International Space Station is usually performed with maximum loads of 70% body weight (0.7 g). However, it has not been investigated how the reduced musculoskeletal loading affects muscle and series elastic element dynamics, and thereby force and power generation. Therefore, this study examined the effects of running on the vertical treadmill facility, a ground-based analog, at simulated 0.7 g on gastrocnemius medialis contractile behavior. The results reveal that fascicle-series elastic element behavior differs between simulated hypogravity and 1 g running. Whilst shorter peak series elastic element lengths at simulated 0.7 g appear to be the result of lower muscular and gravitational forces acting on it, increased fascicle lengths and decreased velocities could not be anticipated, but may inform the development of optimized running training in hypogravity. However, whether the alterations in contractile behavior precipitate musculoskeletal degeneration warrants further study.

The mobility limitation in healthy older people is due to weakness and not slower muscle contractile properties

The maximal power generating capacity of a muscle declines with age and has a negative impact on the performance of daily life activities. As muscle power is the product of force and velocity, we recruited 20 young (10 men, 10 women: 20–31 years) and 20 older (10 men, 10 women: 65–86 years) people to investigate which of these components contributes to the lower power and performance in old age. After determination of the maximal isometric knee extension torque (MVC), they performed a countermovement jump (CMJ) in 1) the normal situation (normal), 2) with an extra load of 15% body weight (loaded) and 3) 15% lower body weight (unloaded with a pulley system), and a timed up-and-go test (TUG) in the normal or loaded condition. The TUG and CMJ performance was lower in old than young participants (p<0.001). Below a critical CMJ peak power of ~23.7 W·kg^-1 TUG showed a progressive decrease. The CMJ take-off velocity (V_off) in the normal condition was lower in old than young participants (p<0.001). However, the V_offvs. body weight/MVC relationship of the normal, loaded and unloaded data combined was similar in the old and young participants and fitted the Hill equation (R² = 0.396). This indicates that 1) only when peak power drops below a critical threshold TUG becomes impaired and 2) there was no evidence for intrinsic slowing of the muscle contractile properties in older people, but rather the older people were working on a slower part of the force-velocity relationship due to weaker muscles.

Gastrocnemius Medialis Contractile Behavior Is Preserved During 30% Body Weight Supported Gait Training

Rehabilitative body weight supported gait training aims at restoring walking function as a key element in activities of daily living. Studies demonstrated reductions in muscle and joint forces, while kinematic gait patterns appear to be preserved with up to 30% weight support. However, the influence of body weight support on muscle architecture, with respect to fascicle and series elastic element behavior is unknown, despite this having potential clinical implications for gait retraining. Eight males (31.9 ± 4.7 years) walked at 75% of the speed at which they typically transition to running, with 0% and 30% body weight support on a lower-body positive pressure treadmill. Gastrocnemius medialis fascicle lengths and pennation angles were measured via ultrasonography. Additionally, joint kinematics were analyzed to determine gastrocnemius medialis muscle-tendon unit lengths, consisting of the muscle's contractile and series elastic elements. Series elastic element length was assessed using a muscle-tendon unit model. Depending on whether data were normally distributed, a paired t-test or Wilcoxon signed rank test was performed to determine if body weight supported walking had any effects on joint kinematics and fascicle-series elastic element behavior. Walking with 30% body weight support had no statistically significant effect on joint kinematics and peak series elastic element length. Furthermore, at the time when peak series elastic element length was achieved, and on average across the entire stance phase, muscle-tendon unit length, fascicle length, pennation angle, and fascicle velocity were unchanged with respect to body weight support. In accordance with unchanged gait kinematics, preservation of fascicle-series elastic element behavior was observed during walking with 30% body weight support, which suggests transferability of gait patterns to subsequent unsupported walking.

Hopping in hypogravity-A rationale for a plyometric exercise countermeasure in planetary exploration missions

Moon and Mars are considered to be future targets for human space explorations. The gravity level on the Moon and Mars amount to 16% and 38%, respectively, of Earth’s gravity. Mechanical loading during the anticipated habitual activities in these hypogravity environments will most likely not be sufficient to maintain physiological integrity of astronauts unless additional exercise countermeasures are performed. Current microgravity exercise countermeasures appear to attenuate but not prevent ‘space deconditioning’. However, plyometric exercises (hopping and whole body vibration) have shown promise in recent analogue bed rest studies and may be options for space exploration missions where resources will be limited compared to the ISS. This paper therefore tests the hypothesis that plyometric hop exercise in hypogravity can generate sufficient mechanical stimuli to prevent musculoskeletal deconditioning. It has been suggested that hypogravity-induced reductions in peak ground reaction force (peak vertical GRF) can be offset by increases in hopping height. Therefore, this study investigated the effects of simulated hypogravity (0.16G, 0.27G, 0.38G, and 0.7G) upon sub-maximal plyometric hopping on the Verticalised Treadmill Facility, simulating different hypogravity levels. Results show that peak vertical GRF are negatively related to simulated gravity level, but positively to hopping height. Contact times decreased with increasing gravity level but were not influenced through hopping height. In contrast, flight time increased with decreasing gravity levels and increasing hopping height (P < 0.001). The present data suggest that the anticipated hypogravity-related reductions of musculoskeletal forces during normal walking can be compensated by performing hops and therefore support the idea of plyometric hopping as a robust and resourceful exercise countermeasure in hypogravity. As maximal hop height was constrained on the VTF further research is needed to determine whether similar relationships are evident during maximal hops and other forms of jumping.

Involvement of the heparanase procoagulant domain in bleeding and wound healing

Essentials Heparanase forms a complex with tissue factor and enhances the generation of factor Xa. The present study was aimed to identify the procoagulant domain of heparanase. Procoagulant peptides significantly shortened bleeding time and enhanced wound healing. Tissue factor pathway inhibitor (TFPI)-2 derived peptides inhibited the procoagulant peptides.

SUMMARY

Background Heparanase, which is known to be involved in angiogenesis and metastasis, was shown to form a complex with tissue factor (TF) and to enhance the generation of activated factor X (FXa). Our study demonstrated that peptides derived from TF pathway inhibitor (TFPI)-2 impeded the procoagulant effect of heparanase, and attenuated inflammation, tumor growth, and vascularization. Aims To identify the procoagulant domain in the heparanase molecule, and to evaluate its effects in a model of wound healing that involves inflammation and angiogenesis. Methods Twenty-four potential peptides derived from heparanase were generated, and their effect was studied in an assay of FXa generation. Peptides 14 and 16, which showed the best procoagulant effect, were studied in a bleeding mouse model and in a wound-healing mouse model. Results Peptides 14 and 16 increased FXa levels by two-fold to three-fold, and, at high levels, caused consumption coagulopathy. The TFPI-2-derived peptides explored in our previous study were found to inhibit the procoagulant effect induced by peptides 14 and 16. In the bleeding model, time to clot formation was shortened by 50% when peptide 14 or peptide 16 was topically applied or injected subcutaneously. In the wound-healing model, the wound became more vascular, and its size was reduced to one-fifth as compared with controls, upon 1 week of exposure to peptide 14 or peptide 16 applied topically or injected subcutaneously. Conclusions The putative heparanase procoagulant domain was identified. Peptides derived from this domain significantly shortened bleeding time and enhanced wound healing.

Evaluation of noise-induced hearing loss by auditory steady-state and auditory brainstem-evoked responses

OBJECTIVES

Noise-induced hearing loss (NIHL) may result from occupational noise exposures and is considered as an 'Occupational Disease'; therefore, it is compensable. To verify the existence and severity of the work-related hearing loss, there is a need of an objective, reliable auditory measure in cases of arbitration of financial disputes to resolve any medicolegal aspects. The objective of the study was to compare between the ABR and ASSR for predicting the behavioural threshold in subjects with normal hearing or NIHL.

DESIGN

The study included 82 subjects regularly exposed to high levels of occupational noise, with normal hearing and NIHL. ABR to clicks and to tone bursts were recorded followed by multiple-frequency ASSR. Physiological and behavioural thresholds were compared for specific frequencies (1000, 2000 Hz) and average of high-frequency range (2000 and 4000 Hz). In addition, Pearson correlations and the specificity and sensitivity of each measure were also calculated using receiver operating characteristic (ROC) curves.

RESULTS

In the NIHL group, there was a significantly smaller difference between the behavioural threshold and click-ABR than the ASSR in high-frequency range. Pearson correlations were significantly higher for click-ABR. Analysis of specific frequencies yielded a smaller difference between behavioural and ASSR than tone-burst-ABR thresholds, with a slightly better correlation for ASSR than tone-burst-ABR. Higher sensitivity but lower specificity was suggested for ASSR than ABR.

CONCLUSIONS

ASSR is associated with high-frequency specificity, shorter test sessions and good correlations with behavioural thresholds, making it a potentially better measure than ABR for predicting audiograms in subjects with NIHL. These findings have diagnostic implications, especially in cases of workers' compensation when subjects may be uncooperative.

Novel peptides that inhibit heparanase activation of the coagulation system

Heparanase is implicated in cell invasion, tumour metastasis and angiogenesis. It forms a complex and enhances the activity of the blood coagulation initiator - tissue factor (TF). We describe new peptides derived from the solvent accessible surface of TF pathway inhibitor 2 (TFPI-2) that inhibit the heparanase procoagulant activity. Peptides were evaluated in vitro by measuring activated coagulation factor X levels and co-immunoprecipitation. Heparanase protein and/or lipopolysaccharide (LPS) were injected intra-peritoneally and inhibitory peptides were injected subcutaneously in mouse models. Plasma was analysed by ELISA for thrombin-antithrombin complex (TAT), D-dimer as markers of coagulation activation, and interleukin 6 as marker of sepsis severity. Peptides 5, 6, 7, 21 and 22, at the length of 11-14 amino acids, inhibited heparanase procoagulant activity but did not affect TF activity. Injection of newly identified peptides 5, 6 and 7 significantly decreased or abolished TAT plasma levels when heparanase or LPS were pre-injected, and inhibited clot formation in an inferior vena cava thrombosis model. To conclude, the solvent accessible surface of TFPI-2 first Kunitz domain is involved in TF/heparanase complex inhibition. The newly identified peptides potentially attenuate activation of the coagulation system induced by heparanase or LPS without predisposing to significant bleeding tendency.

Transient Deafness in Young Candidates for Cochlear Implants

This study describes 5 infants who were diagnosed with auditory neuropathy (AN) associated with severe to profound neural hearing loss shortly after birth. However, on repetition of the tests 7-12 months later, all infants showed full or partial recovery. The follow-up electrophysiological patterns were characterized by the appearance of wave I, followed by wave III and V, reflecting synchronization of auditory pathways and improvement in auditory nerve function. Suspected causative or contributory factors were neonatal hyperbilirubinemia, hypoxia, ischemia, and central nervous system immaturity, alone or in combination. These findings indicate that lack of an auditory brain stem response does not necessarily mean no hearing and that the situation where AN exists can improve. Thus, clinicians should be made aware that although cochlear implants may yield better auditory performance when applied early, they should be considered a therapeutic option only after repeated measures have proved persistent AN, and no child should be considered for an implant until a behavioral measure of hearing has been obtained.

The prevalence of congenital and early-onset hearing loss in Jordanian and Israeli infants

The objective of the study was to investigate the prevalence of congenital and early-onset hearing loss, and the influence of the known risk factors for hearing loss on infants in Jordan and Israel. Subjects were a total of nearly 17,000 infants from both countries, including infants with and without risk factors for hearing loss. The hearing screening protocol included distortion product otoacoustic emission, followed in case of repeated OAE referral or high risk (HR) infant by diagnostic auditory brainstem responses. The results indicate that the prevalence and severity of hearing loss amongst Jordanian infants (1.37%) is remarkably higher as compared to the Israeli infants (0.48%). The overall prevalence of bilateral SNHL was seven times more in the Jordanian infants, 18 times in non-risk, and three times in the HR infants relative to the Israeli infants. Risk factors including family history, hyperbilirubinemia, bacterial meningitis, and associated syndromes were more prevalent amongst Jordanian infants. This unique study underscores the importance of sharing and exchanging information to create empirical data to guide health-care providers in adapting protocols to the local constraints in developing countries.

Hyperacusis in Williams syndrome: Characteristics and associated neuroaudiologic abnormalities

BACKGROUND

Hyperacusis and phonophobia are common, debilitating symptoms in Williams syndrome (WS), yet little is known about their underlying audiologic and neurologic processes.

METHODS

The mothers of 49 subjects with WS were asked to complete the Hyperacusis Screening Questionnaire. Subjects with reported hyperacusis and sufficient developmental capacity underwent comprehensive audiological and brain auditory evoked response (BAER) testing. Findings were compared with those from pair-matched typically developing control subjects.

RESULTS

Forty-one of the 49 children with WS (84%) had hyperacusis of moderate to severe degree, which began in infancy. Of these, 21 (mean age 15.8 +/- 5.5 years) were quantitatively tested. Subjects with WS reported discomfort at sound intensities on average 20 dB lower than control subjects. Pure-tone audiometry and distortion products otoacoustic emission test revealed a high-frequency cochlear hearing loss. An absence of ipsilateral acoustic reflex responses to maximum stimulation was significantly more common in the subjects with WS than controls. On BAER testing, the WS group had a significant prolongation in wave I latency.

CONCLUSIONS

Hyperacusis in Williams syndrome (WS) is associated with a high-frequency hearing loss resembling the configuration of noise-induced hearing loss. The hyperacusis and hearing loss in WS may stem from a deficiency in the acoustic reflex resulting from auditory nerve dysfunction. Additional mechanisms that may mediate hyperacusis in WS and should be evaluated in future studies include recruitment, malformation of the facial canal, and haploinsufficiency of the elastin gene.

Dysfunction of the auditory efferent system in patients with traumatic brain injuries with tinnitus and hyperacusis

OBJECTIVES

Tinnitus, hyperacusis and difficulty listening in background noise are common symptoms reported by patients with traumatic brain injury (TBI). The aim of this study was to explore the function of the auditory system in TBI patients with and without auditory complaints but having normal pure-tone audiograms.

METHODS

The study consisted of 24 TBI patients with and 10 TBI patients without auditory complaints. In addition, 15 normal controls were included in the study. The function of the auditory system was tested by recording transient otoacoustic emissions (TEOAE) during the presentation of increasing levels of white noise in the contralateral ear.

RESULTS

Most of the TBI patients with auditory complaints (87%) showed absent or significantly reduced effect of the auditory efferent system as compared with the TBI patients without auditory complaints and to normal controls. However, the global amplitude of the TEOAE was significantly higher in TBI patients with auditory complaints compared to those without.

CONCLUSIONS

Due to its role in peripheral and central auditory activity, dysfunction of the efferent system may be at least partially responsible for these auditory complaints. This study underscores the importance of testing and evaluating the functional integrity of the medial efferent system by an objective and non-invasive method in patients with TBI.

Reduction in noise-induced temporary threshold shift in humans following oral magnesium intake

A previous study demonstrated the prophylactic effects of magnesium on noise-induced permanent threshold shift in humans. For the first time, this study explores the effects of magnesium on temporary threshold shift in 20 human subjects, all men (16-37 years, mean age 21 years). The study was conducted in a double-blind manner on the same subjects tested in three different phases (placebo, magnesium, no-drug). The cochlear changes were assessed using both behavioural (audiograms) and objective (otoacoustic emission) measures. Blood samples were collected at the beginning and end of each phase. Amongst subjects and phases, magnesium intake was associated with significantly lower temporary threshold shift, compared with the other two phases, which were reflected both by the behavioural and cochlear measures. A correlation was found between the blood magnesium levels and temporary threshold shift reduction. No side-effects were associated with the oral ingestion of the magnesium. Magnesium provides significant protection against temporary threshold shift, complementing the previous permanent threshold shift human study. Both human noise-induced hearing loss studies introduced a novel, biological, natural agent for prevention and possible treatment of noise-induced cochlear damage in humans.

Monitoring of the sciatic nerve during hamstring lengthening by evoked EMG

Traction injury to the sciatic nerve can occur during hamstring lengthening. The aim of this study was to monitor the influence of hamstring lengthening on conduction in the sciatic nerve using evoked electromyography (EMG).

Ten children with spastic cerebral palsy underwent bilateral distal hamstring lengthening. Before lengthening, the evoked potential was recorded with the patient prone. During lengthening, it was recorded with the knee flexed to 90°, 60° and 30°, and at the end of lengthening with the hip and knee extended.

In all patients, the amplitude of the evoked EMG gradually decreased with increasing lengthening. The mean decrease with the knee flexed to 60° was 34% (10 to 77), and to 30°, 86% (52 to 98) compared with the pre-lengthening amplitude. On hip extension at the end of the lengthening procedure, the EMG returned to the pre-lengthening level.

Monitoring of the evoked EMG potential of the sciatic nerve during and after hamstring lengthening, may be helpful in preventing traction injury.

Pomegranate juice flavonoids inhibit low-density lipoprotein oxidation and cardiovascular diseases: studies in atherosclerotic mice and in humans

The beneficial health effects attributed to the consumption of fruit and vegetables are related, at least in part, to their antioxidant activity. Of special interest is the inverse relationship between the intake of dietary nutrients rich in polyphenols and cardiovascular diseases. This effect is attributed to polyphenols' ability to inhibit low-density lipoprotein (LDL) oxidation, macrophage foam cell formation and atherosclerosis. Pomegranate polyphenols can protect LDL against cell-mediated oxidation via two pathways, including either direct interaction of the polyphenols with the lipoprotein and/or an indirect effect through accumulation of polyphenols in arterial macrophages. Pomegranate polyphenols were shown to reduce the capacity of macrophages to oxidatively modify LDL, due to their interaction with LDL to inhibit its oxidation by scavenging reactive oxygen species and reactive nitrogen species and also due to accumulation of polyphenols in arterial macrophages; hence, the inhibition of macrophage lipid peroxidation and the formation of lipid peroxide-rich macrophages. Furthermore, pomegranate polyphenols increase serum paraoxonase activity, resulting in the hydrolysis of lipid peroxides in oxidized lipoproteins and in atherosclerotic lesions. These antioxidative and antiatherogenic effects of pomegranate polyphenols were demonstrated in vitro, as well as in vivo in humans and in atherosclerotic apolipoprotein E deficient mice. Dietary supplementation of polyphenol-rich pomegranate juice to atherosclerotic mice significantly inhibited the development of atherosclerotic lesions and this may be attributed to the protection of LDL against oxidation.

Ectodermal dysplasia, ectrodactyly and macular dystrophy (EEM syndrome) in siblings

We report a brother and sister with ectodermal dysplasia, ectrodactyly, and macular dystrophy (the EEM syndrome). Both children had abnormalities of the hands and the hair, and bilateral macular degeneration. The clinical picture in both is similar to, but less severe than, that described in the previously reported cases of this rare syndrome. Even though the parents are not related, they are both of Jewish Yemenite origin, and the possibility of a common ancestor cannot be ruled out. This would suggest autosomal recessive inheritance. The clinical picture in these patients suggests either variable expression or genetic heterogeneity in the EEM syndrome and further delineates the clinical and genetic spectrum of this condition.

Anxiety reaction in children during removal of their plaster cast with a saw

We have had experience of an 18-month-old boy with a cardiomyopathy who died a few minutes after removal of his cast with a saw, apparently from a malignant cardiac arrhythmia triggered by anxiety. We therefore examined the anxiety reaction to this method of removal of a plaster cast in 20 healthy children; ten were provided with hearing protectors and ten were not. The level of anxiety was assessed by measuring the heart rate, a known physiological indicator of anxiety, before, during and five minutes after removal of the cast. The noise level was also measured. The results showed a mean increase in heart rate during the procedure of 27.9 beats per minute (bpm) (26.9%) in the children with no hearing protectors and 10.4 bpm (11.1%) in children who used hearing protectors (p < 0.001). Five minutes after the procedure the heart rate had returned to the baseline rate in all patients. We recommend that hearing protectors should be used in children undergoing removal of a plaster cast to decrease the anxiety reaction. If possible, clinicians should avoid the use of a saw for this purpose in children with a cardiomyopathy.

Anxiety reaction in children during removal of their plaster cast with a saw

We have had experience of an 18-month-old boy with a cardiomyopathy who died a few minutes after removal of his cast with a saw, apparently from a malignant cardiac arrhythmia triggered by anxiety. We therefore examined the anxiety reaction to this method of removal of a plaster cast in 20 healthy children; ten were provided with hearing protectors and ten were not. The level of anxiety was assessed by measuring the heart rate, a known physiological indicator of anxiety, before, during and five minutes after removal of the cast. The noise level was also measured. The results showed a mean increase in heart rate during the procedure of 27.9 beats per minute (bpm) (26.9%) in the children with no hearing protectors and 10.4 bpm (11.1%) in children who used hearing protectors (p < 0.001). Five minutes after the procedure the heart rate had returned to the baseline rate in all patients.

We recommend that hearing protectors should be used in children undergoing removal of a plaster cast to decrease the anxiety reaction. If possible, clinicians should avoid the use of a saw for this purpose in children with a cardiomyopathy.

Evaluating children's hearing by DPOAEs at 1-10 kHz

The efficacy of application of DPOAE (distortion product otoacoustic emission) in the evaluation of hearing in children was assessed. 106 children were checked by both DPOAE and ABR. The results show that DPOAE is highly effective in discriminating between hearing disorders and normal hearing. The correct classification rate of normal ears varied between 86.8-96.8% and ears with hearing loss (ABR threshold equal or above 20 dB HL) 87-100%. At the lower frequencies (1-2 kHz) the hit rate was lower. The results of this study suggest that the DPOAE can be used as a rapid hearing screening test for infants and children providing frequency specific information, mostly in the 3-10 kHz frequency range. The effectiveness of DPOAE at 1-10 kHz was evident in children with middle ear dysfunction and in detecting infants with possible high frequency hearing loss. In addition, high frequency DPOAE broadens the range typically available from click-evoked ABR measurements. This information is of increased clinical value not only in terms of speech and language development but also for detecting children who are at high-risk for possible hearing deterioration and who require early intervention.

Attenuation of atherosclerosis in apolipoprotein E-deficient mice by ramipril is dissociated from its antihypertensive effect and from potentiation of bradykinin

We investigated the mechanism of the antiatherosclerotic effect of the angiotensin-converting enzyme (ACE) inhibitor, ramipril, in the apolipoprotein (apo) E-deficient mice. Mice that received a high dose (5 mg/kg/day) of ramipril supplemented in their drinking water for 10 weeks showed reduced aortic lesion size by 75% compared with placebo-treated mice. At this dosage, ramipril significantly reduced blood pressure from 95+/-5 mm Hg before treatment to 68+/-4 mm Hg at the end of the treatment period. Ramipril also increased the resistance of the mouse low-density lipoprotein (LDL) to CuSO4-induced oxidation, as shown by a prolongation of the lag time required for the initiation of LDL oxidation from 90 min in the placebo-treated mice to >180 min in the ramipril-treated mice. Similarly, a reduction in the maximal LDL-associated conjugated dienes after 180 min of oxidation by 250% in comparison with placebo-treated mice was noted. Ramipril (1 mg/kg/day) that was still adequate to reduce their plasma ACE activity and LDL propensity to lipid peroxidation was insufficient to reduce their blood pressure. This dosage also inhibited the progression of atherosclerosis in the apo E-deficient mice by 74%. The contribution of bradykinin potentiation to the ACE-inhibitor action was assessed by cotreatment of ramipril with the bradykinin B2-receptor antagonist, icatibant (HOE-140, 0.5 mg/kg given subcutaneously twice a day) for a period of 10 weeks. HOE-140 had no effects on ACE activity, LDL lipid peroxidation, blood pressure, or atherosclerosis. In combination with ramipril, no additional effect of HOE-140 on LDL oxidation or on atherosclerosis was noted in comparison with ramipril treatment alone. We thus conclude that the antiatherogenic effect of ramipril in E(0) mice is independent of blood pressure reduction and is not mediated by bradykinin. It seems, therefore, that most of its antiatherosclerotic and antioxidative effects are mediated through the inhibition of angiotensin II production.

The angiotensin-converting enzyme inhibitor, fosinopril, and the angiotensin II receptor antagonist, losartan, inhibit LDL oxidation and attenuate atherosclerosis independent of lowering blood pressure in apolipoprotein E deficient mice

OBJECTIVE

To investigate the possible mechanisms of the antiatherosclerotic effects of the angiotensin-converting enzyme (ACE) inhibitor, fosinopril, in apolipoprotein (apo) E deficient mice.

METHODS

Apo E deficient (E0) mice at the age of 8 weeks received either placebo or a high dose (25 mg/kg/d) of fosinopril supplemented in their drinking water.

RESULTS

After 12 weeks of treatment, fosinopril reduced the aortic lesion size by 70%, compared with the placebo group. At this dosage, fosinopril significantly reduced blood pressure from 93 +/- 2 mmHg before treatment to 70 +/- 2 mmHg at the end of the treatment period (P < 0.005). Fosinopril also increased the resistance of the mice plasma low density lipoprotein (LDL) to CuSO4-induced oxidation, as shown by a 90% reduction in the LDL content of malondialdehyde (MDA) and also by a prolongation of the lag time required for the initiation of LDL oxidation (from 100 min in the placebo-treated mice to more than 240 min in the fosinopril-treated mice; P < 0.001). In addition, fosinopril inhibited CuSO4-induced oxidation of LDL that was obtained from the aortas of the treated mice, as shown by an 18% and 37% reduction in the LDL content of lipid peroxides and hydroperoxy-cholesterol linoleate, respectively, compared with the placebo-treated mice (P < 0.01). A low dosage of fosinopril (5 mg/kg/d) that was still adequate to reduce their plasma ACE activity and LDL propensity to lipid peroxidation was insufficient to lower their blood pressure. This dosage also reduced the aortic lesion size in the apo E deficient mice by 40% (P < 0.01).

CONCLUSIONS

The antiatherogenic effects of fosinopril in apo E deficient mice are due not only to blood pressure reduction but also to the direct inhibition of angiotensin II-dependent effects, which are probably also associated with the inhibition of LDL oxidation.

Otological evaluation of newborns who failed otoacoustic emission screening

Early identification of congenital hearing loss and early rehabilitation is extremely important. Otoacoustic emissions (OAE) are an efficient tool for hearing screening. Previous studies using click evoked otoacoustic emissions (CEOAEs) for newborn hearing screening resulted in approximately 70% pass rate, reflecting intact hearing. The aim of our study was to perform a detailed otological evaluation of newborns who failed OAE screening, using otoscopy, tympanometry and ABR. CEOAEs were recorded from 257 newborns prior to their release from the hospital. Those babies who did not pass the CEOAE were examined by DPOAE, otoscopy, tympanometry and ABR, if needed. 73% of all the newborns had CEOAE in both ears. 20% had CEOAE in only one ear. When the test was administered again three days postpartum, the CEOAE pass rate increased; 98% passed in at least one ear. Most of the newborns (84%) who failed had an obstruction of the external ear canal (collapsed ear canal or debris). There was a good correlation between the otoscopy and the tympanometry. Based on the above results, a newborn hearing screening protocol was introduced.

Angiotensin II atherogenicity in apolipoprotein E deficient mice is associated with increased cellular cholesterol biosynthesis

Angiotensin II (Ang II) was shown to be an important risk factor for accelerated atherosclerosis. Inhibition of Ang II action on the arterial wall by blocking its production with angiotensin converting enzyme (ACE) inhibitors, or by blocking binding to its receptors on cells with antagonists was shown to attenuate atherogenesis in animal model of atherosclerosis. We questioned whether Ang II atherogenicity is related to a stimulatory effect of Ang II on macrophage cholesterol biosynthesis. Angiotensin II injected intraperitoneally once a day (0.1 ml of 10(-7) M per mouse) for a period of 30 days, to the apolipoprotein E deficient mice increased the atherosclerotic lesion area by 95% (P < 0.01 vs. control), compared to placebo-injected mice, with no significant effect on blood pressure or on plasma cholesterol levels. On using mouse peritoneal macrophages (MPMs) that were harvested after intraperitoneally injection of Ang II, an increased rate of cellular cholesterol biosynthesis (measured as incorporation of [3H]acetate into cholesterol) by up to 90% (P < 0.01 vs. control) was observed. In mice treated with the ACE inhibitor, Fosinopril (25 mg/kg per day) a reduction in their MPM's cholesterol synthesis by up to 70% (P < 0.01 vs. control) was obtained. In vitro studies in human monocyte-derived macrophages (HMDM), in MPMs from control BALB/c mice, and in J-774 A.1 macrophage-like cell line demonstrated up to 44, 34 and 30% stimulation of macrophage cholesterol biosynthesis, respectively, following cell incubation with 10(-7) M Ang II for 18 h at 37 degrees C. The stimulatory effect of Ang II on macrophage cholesterol biosynthesis could be related to its interaction with the macrophage AT1 receptor, as Losartan (10(-5) M), an AT1 blocker, but not PD 123319 (10(-5) M), an AT2 blocker, prevented the stimulatory effect on macrophage cholesterol synthesis. Furthermore, in cells that lack the AT1 receptor (RAW macrophages), Ang II did not increase cellular cholesterol synthesis. Ang II increased macrophage 3-hydroxy-3-methyl glutaryl CoA (HMG CoA) reductase mRNA levels in a dose dependent manner in J-774 A.1 macrophages and in MPM. Losartan, the AT1 receptor antagonist clearly attenuated this mRNA induction. We thus conclude that Ang II stimulation of macrophage cholesterol biosynthesis is related to its interaction with the AT1 receptor, followed by stimulation of macrophage HMG CoA reductase gene expression, which leads to increased cellular cholesterol biosynthesis, and can possibly result in macrophage cholesterol accumulation and foam cell formation.

Antiatherosclerotic and antioxidative effects of captopril in apolipoprotein E-deficient mice

The effect of the angiotensin-converting enzyme (ACE) inhibitor, captopril, on the development of atherosclerosis was determined in the apolipoprotein (apo) E-deficient mice. These mice develop severe hypercholesterolemia and extensive atherosclerotic lesions on chow diet, similar to those found in humans. Furthermore, in these mice, accelerated atherosclerosis is associated with increased plasma lipid peroxidation, a phenomenon that may play a crucial role in the buildup of the atherosclerotic lesions. Mice received either placebo or 50 mg/kg/day of captopril. After 12 weeks of treatment, captopril reduced the aortic-lesion area by 70% compared with that of the placebo-treated group. Captopril also increased the resistance of low-density lipoprotein (LDL) to CuSO4-induced oxidative stress, as shown by a significant reduction in the LDL content of malondialdehyde (MDA) by 30%, as well as by the prolongation of the lag time required for LDL oxidation from 55 min in the placebo-treated mice to 70 min in the captopril-treated mice, and reduction of the maximum LDL oxidation at 150 min by 35%. In vitro studies demonstrated that preincubation of LDL with captopril, inhibited the onset of CuSO4-induced LDL peroxidation up to 120 min, and reduced the LDL content of MDA by 90%. We conclude that captopril attenuates atherosclerosis in the apo E-deficient mice, and this phenomenon may be related to its inhibitory effect on the plasma LDL oxidation.

Evaluating noise induced hearing loss with distortion product otoacoustic emissions

This study assessed the clinical efficacy of screening for noise induced hearing loss (NIHL) with distortion product otoacoustic emissions (DPOAE). DPOAEs were recorded from 76 military personnel (137 ears) aged between 17 and 41 years in response to equilevel 70 dB SPL primary stimulating tones. The 2f1-f2 DPOAE levels were correlated with audiometric thresholds at frequencies close to f2. Ears with normal audiograms, but with a history of military noise exposure, had DPOAEs that were significantly decreased in amplitude as compared to the ears of normal hearing non-exposed to noise subjects. These ears also had an increased absence of DPOAEs as compared with the ears of the normal hearing non-exposed to noise subjects. Although, in general, the DPOAE amplitudes and spectral frequency ranges reflected the audiometric NIHL configurations, in a number of cases DPOAEs were present for hearing losses up to 75 dB HL. As a consequence, DPOAEs correlated moderately and negatively with the audiometric thresholds. Applying test criteria designed to logically reflect NIHL, DPOAE sensitivity and specificity levels ranged between 0.51-0.90 and 0.63-0.25, respectively. These findings indicate that DPOAEs, recorded and analysed as described, are not sufficiently sensitive to serve as a single test to identify NIHL.

Click evoked otoacoustic emissions: inter-aural and gender differences in newborns

Click evoked otoacoustic emissions (CEOAEs) are an objective and reliable method of assessing cochlear status, particularly suitable for newborns. This study aimed to assess CEOAE inter-aural and gender differences. Other non-auditory factors, such as infant's head size and weight, were considered. Band averaged CEOAEs were analyzed for 120 healthy, full term newborns, 61 females and 59 males. The babies were randomly selected from the nursery and tested in a quiet room away from the ward, using an Otodynamic ILO 92 system. The CEOAEs of the females were significantly larger than those of the males. For the frequency bands 2, 3, and 4 kHz and for the overall response, the emissions were larger in the right ear, for both males and females. These inter-aural differences were more pronounced in male subjects than in female subjects. These findings may reflect the accumulating evidence that differences exist in efferent cochlear inhibition.

Angiotensin II injection into mice increases the uptake of oxidized LDL by their macrophages via a proteoglycan-mediated pathway

Angiotensin II (Ang-II) has been shown to possess several atherogenic properties including its ability to induce macrophage-mediated oxidation of LDL and to form Ang-II-modified LDL which is taken up by macrophages at enhanced rate. Oxidized-LDL (Ox-LDL) is also taken up by macrophages at enhanced rate via several scavenger receptors, leading to macrophage cholesterol accumulation. In the present study we examined the effect of Ang-II on the uptake of Ox-LDL by peritoneal macrophages derived from Balb/c mice (MPM). Intraperitoneal injection of Ang-II (10(-7) M, once daily for a period of 2 days) to the mice resulted in an increased Ox-LDL uptake up to 60%, in comparison to macrophages from placebo-treated mice. Similar results were obtained when Ang-II (10(-7) M) was injected to the mice twice a week for a period of three months. This Ox-LDL uptake was Ang-II dose-dependent. The cellular uptake of acetylated-LDL (Ac-LDL), another ligand for scavenger receptors, however, was not affected by Ang-II injection to the mice. Furthermore, preincubation of the MPM with the monoclonal antibody, anti CD36, reduced macrophage uptake of Ox-LDL in Ang-II-treated mice by only 11%. Ang-II administration to mice resulted in a 60% increase in the macrophage cellular proteoglycan content. Chondroitinase treatment of MPM decreased Ox-LDL cellular uptake by 20% and by 38% in placebo-treated and Ang-II-treated cells, respectively. We thus conclude that Ang-II administration to mice enhances their macrophage Ox-LDL uptake via its stimulating effect on cellular proteoglycan content and this process can lead to foam cell formation and atherosclerosis.

The angiotensin-II receptor antagonist, losartan, inhibits LDL lipid peroxidation and atherosclerosis in apolipoprotein E-deficient mice

The potential antiatherogenic actions of the angiotensin II receptor antagonist, losartan were investigated in apolipoprotein (apo) E deficient mice, an animal model with severe hypercholesterolemia and extensive atherosclerosis. In these animals accelerated atherosclerosis is associated with increased lipid peroxidation which may play a crucial role in the build up of the atherosclerotic lesions. Administration of losartan (25mg/kg/d) to the apo E deficient mice for a 3-month period increased the plasma renin activity 3.5-fold compared to the placebo group. Losartan increased the resistance of LDL to CuSO4-induced oxidative modification as shown by a significant reduction in the LDL content of malondialdehyde by 55% compared to placebo, as well as by the prolongation of the lag time required for LDL oxidation, from 60 min in the placebo-treated mice to more than 140 min in the losartan-treated mice. Losartan reduced significantly the mean atherosclerotic lesion area by 80% compared to the placebo group. We conclude that losartan inhibits LDL lipid peroxidation in the apo E deficient mice and this effect may have an important role in the attenuation of the accelerated atherosclerosis.

Event-related potentials in post-traumatic stress disorder of combat origin

Visual event-related potentials (ERPs) of primary interest in this study of post-traumatic stress disorder (PTSD) were N1, N2, P2, and P3. Forty Israeli combat veterans consisting of 20 PTSD sufferers and 20 normal controls were evaluated. ERPs were recorded in response to three sets of computer-generated visual stimuli, presented in the form of a modified oddball paradigm. These stimuli included: domestic animal pictures (targets), emotionally neutral pictures of furnishings (nontargets), and combat-related pictures (nontarget probes). Subjects were required to discriminate between target and nontarget stimuli by pressing a button in response to target stimuli only. Subjects were instructed to ignore all nontarget stimuli. As expected, target stimuli evoked accentuated P3 amplitudes in both controls and PTSD patients. The nontarget combat-related pictures elicited enhanced P3 and N1 amplitudes in the PTSD patients only. N2 amplitudes were accentuated in PTSD patients for both targets and combat-related pictures. P3 latencies and reaction times to target stimuli were prolonged in PTSD patients. The same tendency was observed for N1 latencies. These results may indicate that an altered state of early and late cognitive selective attention processing exists in PTSD patients in addition to a vulnerability to traumatic reminiscences.

Detailed analysis of auditory brainstem responses in patients with noise-induced tinnitus

The role of the auditory brainstem in tinnitus is questionable. This study aimed comprehensively to assess auditory brainstem responses (ABRs) in patients suffering from noise-induced tinnitus (NIT). ABRs were recorded from 13 chronic NIT patients (21 ears) and 11 (21 ears) age and hearing matched control subjects without tinnitus. ABRs were recorded with scalp electrodes placed ipsilateral and contralateral to the stimulated ear, and in three orthonormal differential configurations. The ABRs were analyzed as a function of time, frequency and voltage space. A significantly enhanced ipsilaterally recorded, time domain wave III amplitude was observed for the tinnitus patients. This finding was not confirmed by any of the other ABR measures, which were indistinguishable between subject groups. Although this may be a spurious result, it nonetheless may point to an alteration in the functioning of the putative wave III auditory brainstem generator, which deserves further study.

Impaired brain processing in noise-induced tinnitus patients as measured by auditory and visual event-related potentials

OBJECTIVES

This study aimed to confirm that the brain processing of auditory stimuli in tinnitus patients is impaired (Attias, Urbach, Gold, & Shemesh, 1993). In addition, possible brain processing dysfunction in response to visual stimuli was assessed.

DESIGN

Auditory and visual event-related potentials (ERPs) and reaction times were recorded in response to a standard oddball target detection paradigm. The subjects consisted of 21 noise-induced chronic tinnitus patients and 21 age- and hearing-matched control subjects without tinnitus.

RESULTS

The tinnitus patients had significantly prolonged latencies for the auditory nontarget ERP components N1, N2, and P3 and for the auditory target ERP P3 component. The auditory P3 component was also significantly reduced in amplitude for both target and nontarget stimuli for the tinnitus patients. The visual P3 target and nontarget components were similarly significantly prolonged in latency for the tinnitus patients. Reaction times to both target and nontarget stimuli were significantly delayed for the tinnitus patients for both stimulus modalities.

CONCLUSIONS

These findings point to a cortical information processing dysfunction in chronic tinnitus patients associated primarily with auditory stimuli. ERPs may provide an objective electrophysiologic tinnitus measure.

The influence of the efferent auditory system on otoacoustic emissions in noise induced tinnitus: clinical relevance

This study demonstrates a clear relationship between noise induced tinnitus (NIT) and efferent neural auditory activity. The effect of contralateral white noise stimulation on click evoked otoacoustic emissions (CEOAEs) was studied in chronic tinnitus sufferers and controls, with and without a noise induced hearing loss (NIHL). For the non-tinnitus controls, increased contralateral white noise intensities resulted in decreased CEOAE amplitudes, irrespective of the hearing configuration. In contrast, the tinnitus patients responded with increased CEOAE amplitudes, particularly at lower contralateral noise intensities. While this was observed for both normal hearing and NIHL tinnitus patients, the effect was more pronounced amongst the normal hearing group. These findings were interpreted as reflecting a global efferent disorder in NIT patients, and are considered clinically relevant to the objective assessment of tinnitus.

Effect of repeated visual traumatic stimuli on the event related P3 brain potential in post-traumatic stress disorder

Post-Traumatic Stress Disorder (PTSD) patients are characterized by a hypersensitivity to traumatic stimuli which may be expressed as an automatic and involuntary cognitive response. Electrophysiologically this can be recorded as an augmented visual P3 (P300) event related potential (ERP). This study examined P3 changes in response to repeated traumatic pictorial stimuli presented in the form of a visual discrimination oddball paradigm to 40 Israeli combat veterans with and without PTSD. Subjects were asked to press a button when target stimuli (domestic animal pictures) appeared, and to ignore all non-target stimuli (irrelevant pictures of furnishings/flowers and traumatic combat related pictures). On average, P3 in response to combat related pictures was earlier and approximately 5 times greater in amplitude for the PTSD patients as compared to the controls. Repeated combat related pictures stimuli presentation resulted in a rapid and appreciable P3 amplitude reduction and latency prolongation. This effect was not observed for the target stimuli. These findings suggest that a gradually reduced amount of attentional resource is required and allocated to the processing of repeated CRP stimuli. This may occur as a consequence of the activation of an inhibitory mechanism related to the cognitive processing of traumatic stimuli.

Classification of veterans with post-traumatic stress disorder using visual brain evoked P3s to traumatic stimuli

BACKGROUND

Post-traumatic stress disorder (PTSD) typically involves a re-experiencing of traumatic events. In a previous P3 study it was found that PTSD patients react both selectively and involuntarily to combat-related pictures, exhibiting augmented P3 event-related potentials and thus providing a brain activity measure. The clinical application of these findings in differentiating PTSD patients from controls was tested.

METHOD

Twenty Israeli combat veterans suffering from PTSD and 20 age-matched veterans without PTSD were evaluated. P3 potentials were recorded at Pz and Cz in response to visual motor-task target stimuli (pictures of domestic animals), non-target probe stimuli (combat-related pictures), and non-target irrelevant stimuli (pictures of furnishings and flowers).

RESULTS

Using the Fisher Linear Discrimination Method the P3 measures correctly classified 90% of the PTSD patients and 85% of the controls.

CONCLUSIONS

Visual P3s recorded in response to combat-related pictorial stimuli may introduce an efficient tool for studying higher brain activity in PTSD, complementing other behavioural and psychophysiological measurements.

Noise induced temporary otoacoustic emission shifts

Otoacoustic emissions are considered to reflect the outer hair cell activity of the cochlea, which in turn is recognised as the site most affected by noise exposure. The purpose of this study was to assess temporary cochlear alterations following brief noise exposure. Twenty young male subjects were exposed to 10 minutes of white noise at 90 dB SL. Standard pure tone audiometry, along with click and distortion product otoacoustic emissions (CEOAEs and DPOAEs), were measured before and after the noise exposure. Auditory pure tone threshold shifts of the order of 15 dB were accompanied by temporary CEOAE shifts of the order of 3 dB. DPOAE thresholds were elevated by approximately 5 dB. A positive, significant, and relatively strong correlation was obtained between the CEOAE shifts and the pure tone temporary threshold shifts (TTSs). However, in a number of cases emission shifts were unaccompanied by notable TTSs. Emissions appear to be more sensitive to cochlear changes following noise exposure and therefore more appropriate for screening and monitoring ears at risk of noise induced hearing loss (NIHL). The objectivity of the measurements and the short test time required further enhance their usefulness as a cochlear measure.

Noise-induced otoacoustic emission loss with or without hearing loss

The association between audiometric hearing thresholds and click-evoked otoacoustic emission (CEOAE) spectral properties was examined in 129 adult subjects with and without a noise-induced hearing loss (NIHL). Subjects were grouped according to their "beginning of hearing loss frequency" and their exposure to hazardous noise. Emissions were recorded with an ILO88 Otodynamic Analyzer (Version 2.9) used in the default mode. CEOAE levels decreased as the hearing threshold increased at each of the test frequencies (1,2,3, and 4 kHz). At frequencies where hearing thresholds were worse than 20 dB HL, CEOAEs could not be recorded. Thus as the "beginning of hearing loss frequency" decreased, the frequency range of the emissions became narrower. The hearing threshold for which emissions were not recorded varied significantly between subjects, such that even at frequencies where the hearing threshold was 0 dB HL emissions were not always observed. Noise-exposed, normal-hearing subjects had reduced overall CEOAE power with a narrow frequency range as compared with normal-hearing, nonexposed to noise subjects. For our test conditions, the presence of CEOAEs necessarily suggests hearing thresholds of 20 dB HL or less at the corresponding frequency. A lack of emissions does not necessarily indicate hearing thresholds beyond 20 dB HL.

Effect of hypoxemia and ethacrynic acid on ABR and distortion product emission thresholds

Various studies have shown that induction of hypoxemia in animals such that arterial blood oxygen tensions reach 20-30 mm Hg is accompanied by reversible threshold elevations of the auditory nerve-brain-stem evoked response (ABR). In this state, the endocochlear potential (EP) is depressed, causing a smaller potential difference across the hair cells and/or reduced activity of the cochlear amplifier of the outer hair cells. In order to test these possibilities, ABR threshold (an expression of the overall sensitivity of the cochlea) and changes in threshold of the cubic (2f1-f2) distortion product emissions (DPE) (an expression of activity of the cochlear amplifier) were measured in the same cats while the EP was depressed by hypoxemia or by ethacrynic acid. During the episodes of hypoxemia, DPE thresholds were elevated by 10 dB while ABR thresholds were elevated by 22.8 dB. Therefore, it seems that a normal EP is necessary both for normal cochlear transduction (inner hair cells) and for normal cochlear amplification (outer hair cells). The human fetus in utero is relatively hypoxic and there is evidence that its auditory threshold is also similarly elevated. Therefore the threshold elevation in the fetus in utero, estimated to be about 20 dB, is a consequence of both reduced transduction current through the inner hair cells (about 10 dB) and an additional 10 dB reduction in the activity of the cochlear amplifier of the outer hair cells.

Improved detection of auditory P3 abnormality in dementia using a variety of stimuli

The purpose of this study was to test the improved sensitivity of P3 abnormality in the detection of dementia using a variety of auditory stimuli. Improved detection was obtained using auditory stimuli that differed in their cognitive attributes and by using several P3 measures. These measures included P3 latencies and amplitudes relative to pure tone evoked P3s. Fourteen demented patients (mean age 79.2 years) and a matched normative group were tested. Abnormality of P3 latency for pure tone targets was found in ten patients, equivalent to a hit-rate of 72%. The hit-rate could be further increased by using phonemically and phonetically different types of auditory stimuli, thought to vary in their cognitive attributes. These findings underscore the importance of using a variety of stimuli in testing demented patients.

Oxygen diving-induced middle ear under-aeration

Middle ear negative pressure and effusions have been described after oxygen diving. The prevalence, dynamics and pathophysiology of this phenomenon are not clear, and were hence investigated in the present study. Thirty-four oxygen divers with normal otoscopic and tympanometric evaluation participated in the study. The subjects' symptoms were documented, and pneumatic otoscopy and tympanometry were repeated immediately after the completion of a 3 h, 15 feet oxygen dive, and 7 h later on awakening from the night's sleep. Most divers had positive otoscopic findings the morning after the dive, all of which cleared within 4 h of rising. A significant decrease was observed in average middle ear compliance (p = 0.0463, one way ANOVA), and an increase was found in the number of ears with tympanic compliance less than 0.3 ml (p = 0.0001, Kruskal-Wallis non-parametric ANOVA). In addition, 14.7% of the ears had type C, and 27.9% type B tympanograms the morning after the dive (p = 0.0001 chi2). The generalized nature of oxygen-induced middle ear under-aeration, combined with the dynamics of the symptoms and signs observed, make middle ear barotrauma, tympanic cavity oxygen absorption, and middle ear epithelial oxygen toxicity all unlikely explanations. The observed phenomenon and its dynamics might stem from a reversible derangement in a middle ear chemoreceptor reflex arch, which has recently been suggested as regulating middle ear aeration.

Auditory event related potentials in simulated tinnitus

It was previously demonstrated that noise induced tinnitus (NIT) patients have prolonged reaction times and event related potentials (ERPs) that are reduced in amplitude and prolonged in latency. This study considered whether these alterations occurred as a consequence of the competing auditory tinnitus sensation or as a result of a possible cognitive processing dysfunction in NIT patients. ERPs and reaction times (RTs) were recorded in response to a standard oddball auditory target detection paradigm, with and without simulated tinnitus. Tinnitus was simulated using a high tone narrow band noise presented at the forehead via a standard audiometric bone vibrator. The subjects consisted of 19 males suffering from noise induced hearing loss without tinnitus. The latencies and amplitudes of the ERP components N1, P2, N2, and P3, as recorded along the midline scalp sites (Fz, Cz, and Pz) and bilateral temporal sites (C3 and C4), did not differ significantly when recorded with and without simulated tinnitus. Similarly, the associated reaction times did not differ significantly. These findings suggest that the ERP alterations previously reported to exist for NIT patients cannot be explained simply as a consequence of increased task difficulty and cognitive loading due to the tinnitus sound.

Psychological profile of help-seeking and non-help-seeking tinnitus patients

The psychological profile of tinnitus patients who sought treatment (Help-Seeking, HS) was compared with that of patients who did not seek help (non-help-seeking, NHS) and with normal control subjects. Psychological evaluations as well as hearing, tinnitus loudness, and tinnitus pitch were measured. Overall, the psychiatric symptomatology of HS (n = 50) was more severe with poorer effective coping abilities and externalization of locus of control than NHS (n - 50). However, the psychiatric symptomatology of the NHS was remarkably more severe than that in the normals (n = 73) and more like that in the HS even though they did not turn to treatment. Tinnitus loudness was significantly lower in HS than in NHS subjects. The lower the tinnitus loudness, the higher the psychiatric symptomatology. The trend towards subclinical abnormalities in NHS indicates their vulnerability to pathology and this requires the attention of the therapist in order to increase the patient's self-awareness and to suggest preventive coping strategies or relaxation techniques.

Single P100 visual evoked potential analyses in man

Standards evoked potential averaging leads to a loss of information inherent in the moment to moment variability of the amplitude and latency of single evoked potentials. In order to extract this information, attempts were made to develop procedures which would allow recording of single visual evoked potentials in at least a selected group of subjects. In 11 out of 25 non-selected subjects, 43% to 86% of all stimuli (reversal checkerboard pattern elicited single visual evoked potentials (VEP) which were recognized as such by a group of independent observers. The mean amplitude and latency obtained by directly measuring the peak to peak amplitudes and peak latencies of these single VEPs (arithmetic averaging) were compared to those obtained following conventional time-locked averaging of the same data. During long-term continuous stimulation, the arithmetic averaged VEPs increased in amplitude to a steady state while the time-locked averages of the same sets of responses decreased in amplitude. This reduction was found to be closely related to the latency jitter. It may provide a better understanding of the phenomenon of habituation. This finding was confirmed in model single VEPs obtained by summing on-going pre-stimulus EEG activity with a time-locked average VEP stationary wave form. The variability of the true single VEPs was found to be less than the variability of the model single VEPs. The latency and amplitude parameters of the true single VEPs were strongly correlated with each other while those of the model single VEPs were not. These findings show that single VEPs have an inherent variability which may reflect brain processing.

[Psycho-neuro-physiological assessment of post-traumatic stress disorder using event-related potentials]

To evaluate certain aspects of cognitive processing in posttraumatic stress disorder (PTSD), brain event-related potentials, primarily P300, to traumatic stimuli were recorded. 20 Israeli veterans with PTSD of combat origin and matched controls were studied. In a modification of the oddball paradigm, subjects were asked to react to target pictures of traumatic combat-related subjects while ignoring non-target pictures of irrelevant subjects. PTSD patients reacted with an accentuated P300 and prolonged reaction times to the traumatic pictures. In addition, P300 and reaction times to the target pictures were prolonged in PTSD patients as compared to controls. Event-related potentials (P300) to traumatic stimuli can serve as an objective and accurate brain parameter for characterization and diagnosis of PTSD. In addition, it contributes to understanding the pathogenesis of PTSD as a specific impairment in information processing.

Oral magnesium intake reduces permanent hearing loss induced by noise exposure

INTRODUCTION

Following animal experiments where correlations were observed between serum magnesium level and noise-induced permanent hearing threshold shifts (NIPTS), we tested the prophylactic effect of magnesium in human subjects exposed to hazardous noise.

METHODS

Subjects were 300 young, healthy, and normal-hearing recruits who underwent 2 months of basic military training. This training necessarily included repeated exposures to high levels of impulse noises while using ear plugs. During this placebo-controlled, double-blind study, each subject received daily an additional drink containing either 6.7 mmol (167 mg) magnesium aspartate or a similar quantity of placebo (Na-aspartate).

RESULTS

NIPTS was significantly more frequent and more severe in the placebo group than in the magnesium group, especially in bilateral damages. NIPTS was negatively correlated to the magnesium content of blood red cells but especially to the magnesium mononuclear cells. Long-term additional intake of a small dose of oral magnesium was not accompanied by any notable side effect.

CONCLUSION

This study may introduce a significant natural agent for the reduction of hearing damages in noise-exposed population.