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Biomedical subjects

H Ising

Publications and source records attributed to H Ising.

At least 19 recordsLinked to original sources
PubMed1995

Measurement of free magnesium in blood, serum and plasma with an ion-sensitive electrode.

The fraction of total magnesium bound to protein and other substances depends upon the pH. pH-dependency of ionized free magnesium (iMg2+) in serum is expressed by the Siggaard-Andersen equation: iMg2+ (pH) = iMg2+ (7.4) x 10x(7.4 - pH). During preparation of serum or plasma, considerable pH changes occur which have to be corrected on the basis of the above mentioned equation. For pH correction of iMg2+, x < 0.1 has so far been used. However, this is correct only for new Mg(2+)-sensitive electrodes. During the lifetime of Mg2+ electrodes used in the "Microlyte Magnesium" (Kone Instruments, Finland) x increases and x = 0.2 was found to be a suitable approximation for most of the lifetime. By instantaneous iMg2+ measurements in whole blood samples pH changes and the uncertainty of x can be avoided. Dilution of blood by intravenous infusions decreases x nearly proportionally to the decrease of protein concentration in blood. Various methodological influences such as temperature and delay time before centrifugation, storage of serum and venous occlusion were studied. The circadian rhythm of iMg2+ was found to be considerably more pronounced than that of total Mg and was negatively correlated to changes of free fatty acids. To avoid variations of iMg2+ due to circadian changes, blood collection should be carried out between 6 and 10 a.m. The normal range of iMg2+ in blood of 179 healthy subjects was found to be between 0.46 and 0.60 mmol/l and the quotient of free and total Mg between 0.59 and 0.71. The accuracy of "Microlyte Magnesium" (Kone Instruments, Finland) is sufficient in a wide range of iMg2+.

Blood Specimen Collection↗
PubMed1995

[Empirical studies of music listening habits of adolescents. Optimizing sound threshold limits for cassette players and discoteques].

The music habits of 569 pre-teens and teenagers, between 10 and 17 years of age, were examined and exposure to music from portable music players was compared to that in discotheques. Using a questionnaire we determined the length of time spent listening to portable music players and the frequency of disco visits. The individual level of the music heard through portable music players was measured as a free-field corrected short term mean level. The total music exposure (related to 40 hours per week) was calculated from the data and different assumed disco sound levels. We estimated the risk of ear damage according to ISO 1999 standards on the basis of the total music exposure, whereby the mean disco level was varied as a parameter in the range of 95 to 110 dB(A). Taking only the portable music players into account, one can expect that even after 5 years of music, approximately 5% of the total group would have a hearing loss of 20 dB. This percentage clearly rises when additional exposure is given in discotheques having music levels above 100 dB(A). We suggest therefore that for safety reasons the following sound levels should be observed: 90 dB(A) for portable music players and 95 dB(A) for discos. Through adherence to these levels we would expect that 1% of the young people in our study would have a hearing loss > 10 dB, whereas momentary exposure would result in a hearing loss > 10 dB of 10-20%. Therefore we believe that sound level limitations should be enacted immediately for portable music players and in discotheques.

Adolescent↗
PubMed1995

[Sensorineural hearing loss in children starting school. Results of a representative hearing screening study].

Audiograms in the 0.5-6 kHz frequency range were taken, using improved audiometric screening methods, in 2032 children, 6-7 years old, who were undergoing their pre-school medical examinations. In 151 children (7.4%), the threshold for hearing was above 20 dB for at least one frequency. Of these, 82 children (4% of the overall sample) had a hearing impairment defined as a difference of > or = 10 dB between at least one frequency (3, 4 or 6 kHz) and the mean value from 1+2 kHz. This was evaluated as a sensorineural hearing loss. Unilateral losses (lateral difference > or = 10 dB) were more common than bilateral losses (2.5% vs 1.6% of the overall sample). These unilateral hearing losses in the high-frequency range are essentially regarded as the result of playing with impulse-noise producing toys, such as toy guns with caps.

Audiometry, Pure-Tone↗
PubMed1994

Comparative findings on serum IMg2+ of normal and diseased human subjects with the NOVA and KONE ISE's for Mg2+.

It is clear now that although different ionophores for ionized Mg (IMg2+) have been designed by several groups, each of these has a distinctly different KMgCa. In view of this, it is important to determine whether each of these ion selective electrodes (ISE's) yield identical results for IMg2+ in sera from healthy and diseased humans. Using such an approach, we determined, in a blinded-and random manner, IMg2+ with both the NOVA and KONE ISE's for IMg2+ in two independent laboratories. No significant differences were found either for sera from healthy human volunteers or diseased patients. We did, however, note several interesting findings: 1. randomly, selected hospitalized patients exhibit a much higher incidence of abnormalities for IMg2+ (57-71%) than that noted previously for total Mg (TMg) measurements; and 2. coronary heart disease, rectal cancer and multiple sclerosis patients exhibit extracellular deficits in ionized free Mg.

Aged↗
PubMed1994

[Risk of hearing loss caused by listening to music with head phones].

Sound levels of music played from mini-cassette players via headphones were measured in a nonrepresentative group of 681 pupils whose ages were between 10 to 19 years. Each pupil completed a questionnaire giving the total time spent listening to music each day. The pupils set the music levels (free field corrected short time Leq) between 60 dB(A) and 110 dB(A). In the age group from 12-16 years, 10% chose 110 dB(A). Nearly 50% of the total group usually listened to music less than one hour per day, and just less than 10% listened for four or more hours. The energy equivalent of continuous sound pressure level for an exposure time of 8 h per day was for 55% Leq 8 h < 66 dB(A) and for 7% Leq 8 h > 95 dB(A) while 4% had an Leq 8 h > 105 dB(A). Estimation of the expected hearing losses (HL) were based on ISO 1999: about 10% of the total group were predicted to have a HL > 10 dB at 4 kHz after 5 years. After listening to sound in this manner 0.3% were expected to develop hearing losses at age 25 years that would be severe enough to substantially impair speech intelligibility.

Adolescent↗
PubMed1992

Noise-induced hypertension and magnesium in rats: relationship to microcirculation and calcium.

It has been demonstrated that audiogenic stress (AS) can induce elevation of arterial blood pressure (ABP) in animals and humans and that noise-induced hearing loss may be associated with alterations in Mg metabolism. Experiments were designed to determine whether 1) there is a causal relationship among environmental noise stress, serum and vascular tissue (aortas and portal veins) Mg contents, and development of hypertension and 2) such noise-induced hypertension has a microcirculatory basis and what the mechanism may be. Rats maintained on normal Mg-containing diets for 12 wk (plasma [Mg] = 0.96 +/- 0.02 mM) and subjected to AS (85 dB(A), 12 h/day for 8 wk; 95 dB(A), 16 h/day for 4 wk) demonstrated significant elevation in systolic and diastolic ABP; plasma [Mg] showed a 15% deficit, whereas aortic and portal vein muscle exhibited slight reductions in Mg content and elevation in Ca. Moderate and more severely Mg-deficient animals not subjected to AS also exhibited significant elevations in systolic and diastolic ABP; vascular tissue Mg content decreased, whereas Ca content rose. Animals subjected to combined Mg deficiency and AS for 12 wk exhibited the greatest deficits in plasma and vascular muscle Mg and the greatest elevations in systolic and diastolic ABP; vascular tissue Ca contents also showed the greatest increases. In situ measurements of mesenteric arterioles, venules, and precapillary sphincters in the various subgroups revealed that the lower the plasma [Mg], the more constricted the microvessels, and the higher the ABP, the lower the plasma [Mg]. Capillary blood flow velocities were decreased in relation to the degree of plasma Mg deficit.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Annoyance and health risk caused by military low-altitude flight noise.

Effects of noise of low-flying military jet aircraft were investigated from demoscopic and epidemiological points of view. Areas with different low-altitude flight noise exposure were compared with one another as to subjective annoyance, casual blood pressure and ear symptoms. With the same energy equivalent sound pressure level (Leq), the subjective disturbance caused by military low-altitude flight noise was essentially greater than that due to ordinary flight noise (in the neighbourhood of civil airports). A comparison of several areas revealed that frequencies of ear symptoms (tinnitus lasting more than one hour and permanent hearing threshold shifts of greater than 30 dB) were higher only in areas where maximal flight noise levels considerably exceeded 115 dB (A) accompanied by rapid noise level increases. Blood pressure measurements yielded significantly higher values (group difference 9 mm Hg systolic) in girls living in these highly exposed areas. Acoustic limits are proposed with respect to public health.

Adolescent↗
PubMed1990

Acute circulatory effects of military low-altitude flight noise.

Volunteers aged 70 to 89 years living in a senior citizen's home in Haifa were exposed to flight noise via earphones while watching video films. Their blood pressure and heart rates were measured simultaneously. A high-quality recording and reproduction technique was employed. They were exposed to the noise of two to three overflights with Lmax = 99-114 dB(A) and slow sound pressure level increase (aircraft take off) or with Lmax = 95-112 dB(A) and a fast sound pressure level increase (low-altitude flight at high subsonic speed) at intervals of 10 to 15 min. The systolic and diastolic blood pressure was raised at Lmax = 112 dB(A) and high speed level increase at the average of 23 and 13 mmHg, respectively with individual maximal values of about 40 mm Hg (systolic). In order to prevent risks to the subjects' health, the noise exposure was not raised to levels above 112 dB(A) and fast level increase, although Lmax = 125 dB(A) has been measured in 75 m-low-altitude flight areas. The blood pressure response to a repeated single exposure increased in proportion to the preceding noise exposure. At high intensities and fast level increase an up to fourfold reaction intensification was detected in the majority of subjects. This change in reactivity is regarded as the result of sensitization toward the special type of noise and the implications of these observations for the long-term effects of chronic exposure to low-altitude flight noise are considered. On the basis of these results, proposals are made for limiting values for Lmax and for the speed of sound pressure level increase, the implementation of which would lead to a marked reduction in health risks from low-altitude flight noise.

Aged↗
PubMed1990

Correlations between ventricular arrhythmias and electrolyte disturbances after acute myocardial infarction.

Seven 24-hour ECG recordings and blood samples were taken within 3 weeks in 42 patients who had suffered an acute myocardial infarction (AMI). Ca, K and Mg concentrations in serum, and K and Mg in the erythrocytes, were determined by atomic absorption spectroscopy. One half of the patients were infused with 81 mval/day MgSO4 for 3 days. In patients who exhibited intense electrolyte alterations 10-20 days after AMI, there was a significantly higher rate in the frequency of couplets and/or tachycardia in the 2- to 20-day period after AMI. In patients infused with MgSO4, the fluctuation in serum electrolytes and the rate of arrhythmias were significantly reduced.

Aged↗
PubMed1990

Impact of magnesium supplementation on performance data in young swimmers.

We examined whether healthy young swimmers improved performance during emotional and physical stress testing in the laboratory or during competition. Twenty four well trained healthy Caucasian pupils (14 boys and 10 girls, means = 16 years) were randomly treated either with 20 mmol Mg-aspartate-HCl/d or placebo for 3 months. After Mg supplementation serum Mg increased from 0.85 +/- 0.03 to 0.89 +/- 0.06 mmol/litre (P less than 0.05). Mg in red blood cells remained unchanged (4.79 +/- 0.35 mmol/kg dry weight before supplementation and 4.96 +/- 0.27 three months later, P = 0.32) whereas no increase in serum Mg or Mg in red blood cells was found in subjects who received placebo. Student's t test and analyses of variance revealed no significant differences in performance data either in the laboratory or during competition after supplementation with Mg.

Adolescent↗
PubMed1989

[The effect of music in discothèques on hearing ability].

The risk of hearing loss due to exposure to music in discotheques is discussed on the basis of VDI guideline No 2058, Bl 2. The hypothesis of a relationship was investigated in two empirical studies. In 204 pupils aged 13-19 years, a positive statistical relation of the 4 kHz hearing threshold on the music-hearing habits reported was observed. The difference between the extreme groups of noise exposure was approximately 4 dB (p less than 0.05) on a group average. The evaluation of audiograms of 3133 youths aged 16-20 years applying for a job performed during the medical tests required for employment, showed that those young people with a striking internal ear hearing loss of greater than 30 dB in the area of the C5 depression had spent significantly more time in discotheques than those without striking findings.

Adolescent↗
PubMed1989

[Prevention of noise-induced hearing loss].

Noise-induced hearing loss appears to result from energy depletion in the hair cells. Cell membrane permeability is increased in hypomagnesemia, causing Na+ and Ca++ influx, with subsequent increase in energy-dependent ion-pumping. Energy exhaustion is further enhanced by hypomagnesemia-induced vasoconstriction. Dietary supplementation with magnesium was shown to lessen hearing loss in noise-exposed rats. It is postulated that the same mechanisms may act in man and the possible benefit of magnesium supplementation for noise-exposed workers should be investigated.

Animals↗
PubMed1989

Biochemical mechanisms affecting susceptibility to noise-induced hearing loss.

In magnesium (Mg)-deficient rats and guinea pigs, noise-induced hearing loss (NIHL) was found to be correlated to the decrease of Mg in serum and perilymph. Also, in noise-exposed humans, NIHL increased with decreasing serum Mg. During the process of mechanoelectrical transduction within the hair cells in the inner ear, membrane permeability of K+ and Ca2+ will transiently increase. Mg deficiency may additionally increase membrane permeability and, therefore, energy-dependent K+ and Ca2+ turnover. The increased release of catecholamines in Mg deficiency may affect the hair cells, either directly by increasing the intracellular concentration of free Ca2+ and/or indirectly by reducing the blood flow. Also, thromboxane A2, which is increased in Mg deficiency, may reduce the blood flow in the inner ear. By these mechanisms, Mg deficiency may cause energy depletion and irreversible damage to the hair cells.

Animals↗
PubMed1988

Enhanced ototoxicity of gentamicin and salicylate caused by Mg deficiency and Zn deficiency.

In rats, Mg deficiency caused a moderate hearing loss, measured by means of evoked potentials at 10 and 20 kHz, which was repaired after refeeding a normal diet. Application of 700 mg/kg salicylic acid or injection of 5 x 100 mg/kg gentamicin also caused a reversible hearing loss in normally fed rats. Treatment of Zn-deficient rats with salicylic acid produced a stronger although reversible hearing loss than in normally fed salicylate-treated rats. Treatment of Mg-deficient rats with gentamicin induced a strong hearing loss that was nearly complete and irreversible in 9 of 25 rats.

Animals↗