Targeted disruption of the mouse Npal3 gene leads to deficits in behavior, increased IgE levels, and impaired lung function.

The non-imprinted in Prader-Willi/Angelman syndrome (NIPA) proteins are highly conserved receptors or transporters. Translocation of NIPA genes were found in patients with Prader-Willi syndrome, and loss-of-function of the NIPA1 gene was identified in hereditary spastic paraplegia. The family of NIPA-like domain containing (NPAL) proteins is closely related to the NIPA proteins, but to date nothing is known about their function. Here, we could demonstrate that both human NPAL3 and mouse NPAL3 are ubiquitously expressed and encode highly conserved proteins. To further elucidate the function of the Npal3 gene, knockout (Npal3(-/-)) mice were generated. Intensive phenotypic analyses revealed that disruption of the Npal3 gene results in a pleiotropic phenotype. The function of the nervous system was impaired in both mutant males and females which could be demonstrated in behavioral tests. In addition, in NPAL3 mutants the number of NK cells was decreased and changes in IgM, IgG(2), and IgA were observed, indicating that the immune system is also affected. Interestingly, increased IgE levels as well as impaired lung functions were observed in mutant males but not in mutant females. It should be noted that the human Npal3 gene is located at 1p36.12-->p35.1, and atopic diseases were previously linked to this genomic region. Thus, the Npal3(-/-) mice could serve as a valuable model system for studying atopic diseases.

Acute effects of an organic solvent mixture on the human central nervous system.

OBJECTIVES: At workplaces, organic solvents are often used as mixtures. Nevertheless, there is limited knowledge of their acute effects on human central nervous system. Here we report the effects of a toluene-acetone mixture. METHODS: In a parallel design, subgroups of 12 healthy men each were exposed to a mixture containing 25 ppm acetone and 250 ppm toluene or to air (control) in an exposure chamber for 4.5 hours. Concentrations corresponded to the German TLV (TRGS 403). Concentrations of toluene and acetone in venous blood were measured by headspace gas chromatography. Subjects were sedentary. The following tests were performed before and at the end of exposure: Questionnaires, simple reaction time, vigilance, quantitative analysis of EEG with open and closed eyes and during the Color Word Stress test, and visual evoked potentials (VEP). RESULTS: Blood levels were 0.14 (+/- 0.04 SD) mg toluene/l and 5.43 (+/- 1.37 SD) mg acetone/l at the end of solvent exposure. Scores of neurotoxic and irritating symptoms were not elevated during solvent exposure. Exposed subjects performed as well as control subjects on the simple reaction time test and on the vigilance test, neither reaction time nor number of hits differed significantly. A general linear model on log transformed spectral power values showed insignificant changes in EEG. In the alpha subset2-band an average reduction to 86 % was observed in exposed as compared to non exposed subjects with closed eyes, a reduction to 88 % in the theta-band with open eyes, and a reduction to 92 % in the theta-band during the Color Word Stress test. VEP P 100 latencies and amplitudes did not change. CONCLUSION: The mixture consisting of toluene and acetone did not cause any adverse acute effect. With respect to EEG data, possible subclinical effects on central nervous system cannot be excluded.

Cranial nerve function in workers exposed to polychlorinated dioxins and furans.

OBJECTIVE: To look for possible effects of polychlorinated dioxins and furans (PCDD/F) on cranial nerve function. MATERIAL AND METHODS: Clinical and neurophysiological examinations [visual and brainstem auditory evoked potentials (VEP and BAEP), blink reflex] in 121 PCDD/F exposed workers of one pesticide producing plant. RESULTS: BAEP abnormalities were more frequent in workers with chloracne (6 of 33 workers, 18.2%) than in those without chloracne (7 of 84, 8.3%), but this was not statistically significant (chi2: 2.33). VEP abnormalities were seen in one worker with and two without chloracne. Clinically visual functions were normal except in one worker, who was amaurotic since birth. Blink reflex abnormalities without corresponding clinical findings were observed in two patients without chloracne. CONCLUSION: Severe exposure to PCDD/F is not followed by clinical signs of cranial nerve dysfunction but may create an increased risk for abnormal BAEP findings, which were more than twice as common in workers with chloracne. Although this difference did not reach statistical significance, it cannot exclude a toxic effect of PCDD/F, as statistical significance is difficult to achieve with such small numbers of workers. In none of the workers, BAEP abnormalities were accompanied by clinical signs of hearing dysfunction.

Identification of the human ortholog of the t-complex-encoded protein TCTE3 and evaluation as a candidate gene for primary ciliary dyskinesia.

Primary ciliary dyskinesia (PCD) is a heterogeneous autosomal recessive disease that is caused by impaired ciliary and flagellar functions. About 50% of PCD patients show situs inversus, denoted as Kartagener syndrome. In most cases, axonemal defects in cilia and sperm tails can be demonstrated by electron microscopy, i.e. PCD patients often lack inner and/or outer dynein arms in their sperm tails and cilia, supporting the hypothesis that mutations in dynein genes may cause PCD. In order to identify novel PCD genes we have isolated the human ortholog of the murine TCTE3 gene. The human TCTE3 gene encodes a dynein light chain and shares high similarity to dynein light chains of other species. The TCTE3 gene is expressed in tissues containing cilia or flagella, it is composed of four exons and located on chromosome 6q25-->q27. To elucidate the role of TCTE3 as a candidate gene for PCD a mutational analysis of thirty-six PCD patients was performed. We detected five polymorphisms in the coding sequence and in the 5' UTR of the TCTE3 gene. In one patient a heterozygous nucleotide exchange was identified resulting in an arginine to isoleucine substitution at the amino acid level. However, this exchange was also detected in one control DNA. Our results indicate that mutations in the TCTE3 gene are not a main cause of primary ciliary dyskinesia.

Acute effects on the human EEG after an external exposure to 200 ppm methanol.

OBJECTIVES: Even low concentrations of organic solvents may cause acute effects on the human central nervous system. The German MAK (threshold limit value) of methanol is 200 ppm. The aim of this study was to investigate whether acute exposure to 200 ppm methanol causes adverse effects, measured by EEG, and moreover, whether it is possible to differentiate between sedative and excitatory effects with this method. METHODS: Twelve healthy subjects were exposed for 4 h to 200 ppm and to 20 ppm (control) in an exposure chamber in a cross-over design. The EEG was recorded before (reference) and at the end of each exposure with, the subject's eyes closed and opened and during a choice reaction test (color word stress test). Spectral power was calculated by fast Fourier transformation. Subjective symptoms and effects of blinding with 20 ppm methanol were assessed by questionnaires. RESULTS: The study was a single-blind one. During subjects' exposure to 200 ppm, their scores for prenarcotic and irritating symptoms were not different from controls. In the closed-eye condition of subjects, the spectral power of the theta-band and of some electrodes of the delta-band was significantly less at the end of exposure to 200 ppm, than that of controls. In the open-eye condition and during the color word stress test no significant changes were found. CONCLUSION: The changes in the theta-band suggest a slight excitatory effect of 200 ppm methanol. The effect was weak, as scores of acute symptoms did not change. With respect to our results, it is not necessary for the MAK value to be decreased.

Acute effects of 200 ppm 1,1,1-trichloroethane on the human EEG.

OBJECTIVES: Even low concentrations of organic solvents used at work may cause acute effects on the human central nervous system. We investigated the acute effects of 200 ppm 1,1,1-trichloroethane on the human EEG. METHODS: 12 healthy subjects were exposed for 4 hours to 200 ppm and to 20 ppm (control) in an exposure chamber in a cross-over design. EEG was recorded before (reference) and at the end of each exposure with eyes closed and open and during the Color Word Stress test. Spectral power was calculated by Fast Fourier transformation and related to reference values (per cent of baseline). Subjective symptoms and effects of blinding with 20 ppm 1, 1,1-trichloroethane were assessed by questionnaire. RESULTS: Blinding was not effective because of the strong smell of 1,1, 1-trichloroethane. The score for tiredness increased slightly during and after exposure to 200 ppm. In the closed eye condition, the median percentage of spectral power increased at all electrodes of the delta -band, significantly at temporo-occipital leads. In the theta-band, the percentage of the median spectral power was elevated at most of the electrodes but the parietal and some temporal ones. As to the alpha subset1-band, the percentage of the median spectral power was lower at the temporo-parieto-occipital electrodes, yielding significance at T subset4. In the alpha subset2-band, the percentage of the median spectral power was lower at all electrodes, significantly at T subset4 and T subset5. The percentage of the median spectral power of the temporo-parieto-occipital electrodes of the beta subset1 -band was lower during exposure to 200 ppm. There were no clear-cut changes in the beta subset2 -band, in the open eye condition and during the Color Word Stress test. CONCLUSION: The changes in EEG and the increased score for tiredness indicate a slight sedative effect of 200 ppm 1,1,1-trichloroethane.

Saliva as an alternate for blood to measure concentrations of acetone under exposure to isopropanol.

OBJECTIVES: In occupational medicine, blood concentrations are often measured to judge the internal burden of workers at work-place during exposure to a potentially hazardous substance. However, blood-withdrawals are invasive and can often not be taken at work-place due to hygienic reasons. Sampling of saliva is non-invasive and easy to perform even at workplace. In order to substitute blood analysis, analysis of saliva has to be as specific and sensitive as blood investigations. Therefore acetone-concentrations in blood and in saliva during exposure to isopropanol were compared. METHODS: 18 healthy non-smokers were exposed to 360 ppm isopropanol in an exposure chamber over 4 h. Once an hour during exposure and 30 min after, blood and saliva were sampled. Saliva was collected by a cotton plug over 10 minutes and stored in an airtight closed headspace tube. Concentrations of the metabolite acetone were measured by gas chromatography. - RESULTS: The concentrations of acetone in blood and saliva rose continually during exposure and dropped after exposure-cessation. High correlations between concentrations of acetone in blood and saliva were found for each individual and the entire group (entire group: r = 0.8568, p <0.0001, y = 0.8374x - 0.4404). CONCLUSIONS: Acetone-measurement in saliva is a non-invasive, easily conductable and reliable method for estimating the internal burden of isopropanol-exposure. Further studies for the standardization and validation are necessary to impose a threshold limit value on work-place isopropanol-exposure.

[Time zone shift and the immune system during long-distance flights]. / Zeitverschiebung und Immunsystem bei Langstreckenflügen.

Recurrent infections could be seen in frequent flyers indicating an impaired immune reaction after long-distance flights. The increase of the concentration of neopterin points to an activation of the cellular part of the immune system. In combination with the altered differential blood counts, the changes in the proliferation rate of lymphocytes and the immune phenotyping the increase of neopterin leads to an explanation of the down-regulation of the immune system after flights. The mild hypoxia on board of an aircraft triggers an increase of catecholamines and cortisol in serum. Catecholamines lead to a shift of leukocytes from different compartments to the circulating blood and to an activation of immune cells. Cortisol triggers the differentiation of a subgroup of T-Lymphocytes with a rise in TH2-helper cells and a down-regulation of TH1-cells. The latter ones are, however, essential for an induction of a reaction of the cellular immune system and so the function of the cellular part of the immune system will be reduced. If no infection occurs, the concentration of neopterin in serum will drop to normal.

[Time zone shifts and jet lag after long-distance flights]. / Zeitverschiebung und Jet-Lag nach Langstreckenflügen.

Long distance flights with rapid time zone shifts of more than 3 hours lead to a dissociation of the inner circadian clock to the outer pacer. Additionally, the different endogenous circadian rhythms will not longer be synchronized by the endogenous pacer melatonin. This leads to complaints like sleepiness, sleep-disturbances and others. These symptoms are called jet-lag. The subject's performance is disturbed, as well. Different studies showed smaller problems with jet lag when travelling to the west. Since the inner circadian rhythm tends to be 24 up to 26 hours, travelling to the west with a prolongation of the daylight will be tolerated better than flights to the east with a shortening of the day length. Rapid time zone shifts with more than 8 hours to the east lead to individual different ways of resynchronization. Subject either try to adapt to the new time zone by shortening the day (backward adaptation) or they resynchronize forward with a longer duration of adaptation time. Elder subjects with already diminished circadian hormonal rhythm often get more problems concerning symptoms of the jet-lag and in time to recover from the disturbance of the inner clock. No differences can be found between business travelers, tourists and high-performance sportsmen. After flights to the west within 3 to 7 days, most of our inner circadian rhythm will be re-synchronized. After flights to the east, resynchronization can take 5 to 14 days. A symptomatic therapy of jet lag symptoms with a short-acting benzodiazepine like triazolam in a dosage of 12.5 mg or less is well tolerated. A therapy with oral melatonin in a dosage of 0.5 to 5 mg/day given in the evening 1 to 2 hours prior to the desired sleeping-time may be helpful for a group of subjects. Another group of subjects will not have any benefit of a therapy with melatonin, but cannot be defined in advance. A recommendation for a therapy with melatonin to treat jet lag symptoms cannot be given at the moment, since scientific data are still missing. Additionally, the same contaminants, which caused some deaths, as in the related substance tryptophan has been found in some tablets of melatonin.

The exposure of healthy volunteers to 200 ppm 1,1,1-trichloroethane increases the concentration of proinflammatory cytokines in nasal secretions.

OBJECTIVES: Irritating effects of organic solvents have usually been measured by means of questionnaires. The aim of the present study was to evaluate the sensitivity of different methods of detecting subclinical irritating effects. METHODS: Twelve healthy, non-smoking students were exposed to 200 ppm and to 20 ppm 1,1,1-trichloroethane in an exposure chamber, using a crossover design. The amounts of interleukins (IL)-1beta, IL-6 and IL-8 and prostaglandin E(2) (PGE(2)) in nasal secretions were measured. Mucociliary transport time was determined with the saccharine test. Ciliary beat frequency of nasal epithelial cells was measured with video-interference contrast microscopy. Subjective symptoms were assessed by questionnaire. RESULTS: Concentrations of ILs were significantly elevated after exposure to 200 ppm 1,1,1-trichloroethane (IL-1beta 82.4 vs. 28.8 pg/ml (medians), P=0.003; IL-6 12.2 vs. 7.2 pg/ml, P=0. 01; IL-8 549 vs. 424 pg/ml, P=0.007), whereas the other parameters remained unchanged. CONCLUSION: The interleukins measured proved to be sensitive indicators of irritating effects of 1,1, 1-trichloroethane. The German threshold limit (MAK value) of 200 ppm 1,1,1-trichloroethane does not prevent the subclinical inflammation of nasal mucosa.

Increased risk of sensory neuropathy in workers with chloracne after exposure to 2,3,7,8-polychlorinated dioxins and furans.

OBJECTIVE: The existence of a peripheral neuropathy after exposure to polychlorinated dioxins (PCDD) is still discussed, as studies concerning dioxin effects on the peripheral nervous system are rare and contradictory. MATERIAL AND METHODS: Clinical and neurophysiological examinations (motor conduction velocity of the peroneal nerve, sensory conduction velocities of the sural and ulnar nerves) were made in 156 dioxin exposed workers (42 with, 114 without cloracne) from one pesticide producing plant. Because of known risk factors for peripheral neuropathy, 7 workers with and 28 without cloracne were excluded from further analysis. RESULTS: Workers with chloracne had a significantly higher exposure against PCDD as documented by back calculated lipid levels. They complained significantly more often of sexual impotence (28.6% compared to 5.8% of workers without chloracne, P<0.001), had significantly more frequent clinical signs of a sensory neuropathy (= abnormal sensory findings plus deep tendon reflex abnormalities) restricted to the legs (17.1% compared to 1.2%, P<0.001), had significantly more frequent > or =2 neurophysiologic abnormalities (34.3% compared to 14.0%, P<0.025), and had significantly lower mean amplitudes of the motor compound muscle potential of the peroneal nerve. CONCLUSION: PCDD has a mild toxic effect on the peripheral nervous system manifesting as mild sensory neuropathy of the legs in a minority of the most severely exposed persons.

[Obstructive sleep apnea syndrome caused by occupational exposure to solvents]. / Obstruktives Schlafapnoesyndrom durch eine berufliche Lösungsmittelexposition.

HISTORY AND ADMISSION FINDINGS: A 52-year-old man working in a chemical laboratory was referred with the possible diagnosis of toxic encephalopathy. For 17 years he had been exposed to high concentrations of perchlorethylene and n-butanol vapours which every day had caused acute symptoms of organic solvent intoxication. Current complaints were autonomic nervous system symptoms, loss of concentration and memory, and fatigue in the second half of the day. The patient was obese but in good general condition. INVESTIGATIONS: Neuropsychiatric examination confirmed the reported loss of concentration and planning ability at work. The polysomnogram indicated an increased number of largely obstructive apnoea attacks. DIAGNOSIS, TREATMENT AND COURSE: As the patients had an obstructive type of sleep apnoea treatment consisted of positive pressure ventilation at night and weight reduction. The occupational exposure to organic solvents was the likely cause. CONCLUSIONS: As the symptoms of encephalopathy and sleep apnoea syndrome overlap, the latter should be considered before an encephalopathy is diagnosed. Because a rare cause of the sleep apnoea syndrome is prolonged and marked occupational exposure to organic solvents this should be asked about in taking the history. If indeed there has been occupational exposure, it should cease at once and be reported.

Effects of high doses of toluene on color vision.

High exposure to toluene may cause optic neuropathy and retinopathy, both associated with dyschromatopsia. Another solvent, ethanol, is known to induce acute blue-yellow dyschromatopsia. This study investigated the acute effects of high doses of toluene on color vision. Eight male printshop workers were examined before and after cleaning printing containers with pure toluene. After cleaning, concentrations of toluene in blood were between 3.61 and 7.37 mg/l. Color vision was tested with the Farnsworth panel D-15 test, the Lanthony desaturated panel D-15 test, and the Standard Pseudoisochromatic Plates part 2. For control of possible acute effects, eight workers of a metal-working factory without any neurotoxic exposure were tested according to the same procedure. Acute exposure to toluene did not cause impairment of color vision. However, statistical power is limited due to the small number of exposed subjects. Color vision of the printshop workers tested before cleaning was slightly impaired (statistically not significant) when compared with unexposed subjects.

[Anosmia caused by inhaled hazardous substances. Significance for expert assessment general practice]. / Riechstörungen durch inhalative Schadstoffexposition. Bedeutung für die gutachterliche Praxis.

BACKGROUND: Both environmental and occupational pollutants can affect the functional integrity of the olfactory epithelium or even destroy olfactory tissue. However, occupational hyposmia and anosmia have not been included into the list of occupational diseases. Therefore, compensation of occupationally induced smell disorders is difficult. OBJECTIVE: To evaluate patients with toxic hyposmia for the pollutants involved and to discuss consequences for occupational and environmental medicine. METHODS: A total of 19 patients were evaluated in our departments between 1993 and 1997 for olfactory disorders related to environmental or occupational pollutants. The charts of these patients were retrospectically analyzed and the causative pollutants compared with the literature. RESULTS: A chronical exposure to mixtures of metal dusts and steam, volatile organic substances, and anorganic gases were the most common pollutants involved in occupational dysosmia. Only one case of acute development of an anosmia due to exposure to CO and combustion gases was documented. CONCLUSIONS: Olfactory disorders are underestimated in occupational and environmental medicine. Relevance of olfactotoxic substances for occupational medicine can be postulated in metal and chemical workers, in welding and disinfection. The list of occupational diseases should be completed by olfactory hyposmia and anosmia.

Immunologic findings in workers formerly exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin and its congeners.

One hundred ninety-two workers in a German pesticide factory who were exposed to polychlorinated dibenzodioxins and -furans (PCDD/PCDF) were investigated for former and present diseases and laboratory changes of the immune system. Moreover, in a subgroup of 29 highly exposed and 28 control persons, proliferation studies were performed. In addition to assays such as blood count, immunoglobulins, serum electrophoresis, monoclonal bands, surface markers, autoantibodies, and lymphocyte proliferation, two new methods, the rise of tetanus antibody concentration after vaccination and the in vitro resistance of lymphocytes to chromate, were used to diagnose the morphologic and functional state of the immune system. There was no stringent correlation of actual PCDD/PCDF concentrations with the occurrence of infections or with one of the immune parameters. In addition, outcomes of the tetanus vaccination and the chromate resistance test were not correlated with PCDD/PCDF. However, the chromate resistance of lymphocytes stimulated by phytohemagglutinin of highly exposed persons was significantly lower than that for the control group. These findings indicate that the function of lymphocytes can be stressed and possibly impaired by high exposure to PCDD/PCDF.

Elimination of beta-hexachlorocyclohexane in occupationally exposed persons.

The elimination of beta-hexachlorocyclohexane (beta-HCH) in humans was investigated in a group of 40 former workers of a lindane-producing plant by analyzing at least 2 blood specimens (3 specimens in 3 workers) from different time points. Assuming a first-order kinetic model for excretion, the median half-life of beta-HCH is 7.2 yr calculated by concentrations in whole blood and 7.6 yr calculated by concentrations in extractable lipids. In univariate analyses an influence of age, percent body fat, and liver disease (additionally in whole blood an influence of contents of extractable lipids) on clearance was observed. All factors show a positive correlation with half-life. According to a multiple regression model, influence of percent body fat calculated according to Deurenberg et al. (1991) is an important covariate in the description of the variations of the clearance rate (calculated on the basis of extractable lipids) of beta-HCH. The data support the assumption of first-order kinetics.

Blue-yellow deficiency in workers exposed to low concentrations of organic solvents.

OBJECTIVES: To evaluate the effects of low concentrations of organic solvents on color vision. METHODS: Color vision was examined in 24 workers exposed to mixtures of solvents and in 24 control subjects. Exposure to mixtures was below the threshold-limit values. Color vision ability was assessed using the Ishihara plates (to screen for congenital dyschromatopsia), the Farnsworth panel D-15 test, the Lanthony desaturated panel D-15 test, and the Standard Pseudoisochromatic Plates part 2 (SPP2 test). RESULTS: The comparatively less sensitive Farnsworth panel D-15 test failed to show any difference between the groups, but the Lanthony panel D-15 desaturated test as well as the SPP2 test showed a significant impairment in the exposed group. Errors were of the blue-yellow type. CONCLUSION: This study gives further evidence that even mixtures of organic solvents at concentrations below the threshold-limit values may impair color vision.

Elimination of polychlorinated dibenzo-p-dioxins and dibenzofurans in occupationally exposed persons.

The elimination of 2,3,7,8-substituted polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) was investigated in a group of n = 43 exposed workers with 2 blood measurements and n = 5 workers with 3 measurements. Under the assumption of a one-compartment, first-order kinetic model the median half-life for 2,3,7,8-TCDD was 7.2 yr, while for the other dioxins the estimates were between 3.7 yr for 1,2,3,4,6,7,8-HpCDD (hepta-chlorinated) and 15.7 yr for 1,2,3,7,8-PCDD (penta-chlorinated). For the furans median half-lives between 3.0 yr for 1,2,3,4,6,7,8-HpCDF and 19.6 yr for 2,3,4,7,8-PCDF were observed. There was no indication for a deviation from a first-order kinetic. Increasing age and percent body fat were associated with increasing half-life for most of the congeners. Smokers in general had a faster decay than non- and ex-smokers. In summary, the higher chlorinated PCDD/F like TCDD appear to be highly persistent in humans with half-lives ranging between 4 and 12 yr.