Regulation of intracellular membrane interactions: recent progress in the field of neurotransmitter release

Maintenance of compartmental independence and diversity is part of the blueprint of the eukaryotic cell. The molecular composition of every organelle membrane is custom tailored to fulfill its unique tasks. It is retained by strict sorting and directional transport of newly synthesized cellular components by the use of specific transport vesicles. Temporally and spatially controlled membrane fission and fusion steps thus represent the basic process for delivery of both, membrane-bound and soluble components to their appropriate destination. This process is fundamental to cell growth, organelle inheritance during cell division, uptake and intracellular transport of membrane-bound and soluble molecules, and neuronal communication. The latter process has become one of the best studied examples in terms of regulatory mechanisms of membrane interactions. It has been dissected into the stages of transmitter vesicle docking, priming, and fusion: Specificity of membrane interactions depends on interactions between sets of organelle-specific membrane proteins. Priming of the secretory apparatus is an ATP-dependent process involving proteins and membrane phospholipids. Release of vesicle content is triggered by a rise in intracellular free Ca2+ levels that relieves a block previously established between the membranes poised to fuse. Neurotransmitter release is a paradigm of highly regulated intracellular membrane interaction and molecular mechanisms for this phenomenon begin to be delineated.

What makes a child allergic? Analysis of risk factors for allergic sensitization in preschool children from East and West Germany

Earlier epidemiologic studies within Germany found a higher frequency of allergic sensitization in West Germany. The reasons for that and the role of environmental factors in the process of allergic sensitization are not fully understood. This study aimed to determine the prevalence of positive skin-prick test results 5 years after unification and to investigate risk factors for allergic sensitization in preschool children. A total of 1235 children (5-6 years) from two West and five East German locations were skin-prick tested after the compulsory school entrance examination. Six common aero- (birch, grass, mugwort pollen, cat, HDM, alternaria) and two food allergens (egg, milk) were used and additional information was obtained by questionnaire. Of the tested children 23.3% exhibited at least one positive reaction. The prevalence of sensitization to the single allergens was as follows: grass (14.4%), birch (6.6%), mugwort pollen (4.5%), cat (8.5%), HDM (5.5%), alternaria (4.9%), egg (2.8%), and milk (3.9%). In the crude analysis significantly more children were sensitized in the East German city Magdeburg (40.2%) compared to the West German control region Borken (23.5%) (OR 2.20, CI 1.47-3.29). Dampness and visible molds were reported in 8.8% of all households, but significantly more often for East German apartments (10.3% versus West Germany 1.9%, OR 5.85, CI 2.55-16.53). Dampness and molds were associated with a higher frequency of sensitizations (40.6% versus 27.6% in unaffected homes). After controlling for sex, parental atopy, SES, family size, and smoking during pregnancy, this association remained statistically significant (OR 1.93, CI 1.19-3.12). With regard to single allergens, dampness and visible molds were significantly associated with sensitization to HDM (OR 3.37, CI 1.63-6.96), cat (OR 3.19, CI 1.11-5.74), and mugwort pollen (OR 2.86, CI 1.29-6.35). In addition, family size was inversely and linearly associated with the frequency of sensitization (OR for four, three, and two-person households: 1.10 (0.74-1.63), 1.57 (1.06-2.42), 2.70 (1.39-5.24), respectively, when compared to family size of five or more). Neither parental predisposition for atopic diseases nor parental education level influenced the prick test reactivity. We conclude that in addition to genetic predisposition, environmental factors like indoor climate and probably infectious stimuli (family size) play an important role in the process of allergic sensitization in children.

Respiratory changes associated with rapid eye movements in normo- and hypercapnia during sleep

Rapid eye movements during rapid-eye-movement (REM) sleep are associated with rapid, shallow breathing. We wanted to know whether this effect persisted during increased respiratory drive by CO2. In eight healthy subjects, we recorded electroencephalographic, electrooculographic, and electromyographic signals, ventilation, and end-tidal PCO2 during the night. Inspiratory PCO2 was changed to increase end-tidal PCO2 by 3 and 6 Torr. During normocapnia, rapid eye movements were associated with a decrease in total breath time by -0.71 +/- 0.19 (SE) s (P < 0.05) because of shortened expiratory time (-0.52 +/- 0.08 s, P < 0.001) and with a reduced tidal volume (-89 +/- 27 ml, P < 0.05) because of decreased rib cage contribution (-75 +/- 18 ml, P < 0.05). Abdominal (-11 +/- 16 ml, P = 0.52) and minute ventilation (-0.09 +/- 0.21 ml/min, P = 0.66) did not change. In hypercapnia, however, rapid eye movements were associated with a further shortening of total breath time. Abdominal breathing was also inhibited (-79 +/- 23 ml, P < 0.05), leading to a stronger inhibition of tidal volume and minute ventilation (-1.84 +/- 0.54 l/min, P < 0.05). We conclude that REM-associated respiratory changes are even more pronounced during hypercapnia because of additional inhibition of abdominal breathing. This may contribute to the reduction of the hypercapnic ventilatory response during REM sleep.

The influence of cultural and educational factors on the validity of symptom and diagnosis questions for atopic eczema

Valid questions for atopic eczema are necessary to identify risk factors in epidemiological studies. We have examined the influence of cultural and educational factors on the validity of some questions on atopic eczema used in the International Study of Asthma and Allergies in Childhood by using data from a cross-sectional study on 1511 children aged 6 years from East and West Germany. We tested three questions in relation to a point prevalence of atopic eczema as recorded by a dermatologist: (i) has a physician ever diagnosed eczema in your child? (ii) Has your child ever had an itchy rash which came and went for at least 6 months? (iii) Has your child ever had 'neurodermatitis' (atopic eczema, endogenous eczema)? The point prevalence of atopic eczema on the day of investigation was 11.1% (134 of 1217). According to the questionnaire, 15.7% of the children had had physician-diagnosed eczema, 14.1% had had neurodermatitis and 11.3% had had an itchy rash for > 6 months. Fifty-one per cent of parents who had a child with atopic eczema on the day of investigation said that their child had had an itchy rash which came and went for at least 6 months. This sensitivity value is less than that found in another community survey conducted in the U.K., suggesting that the German wording of the question seems to mean something more severe to the parents than the English one. The education of the parents had an influence on the validity of the three questions: parents with < 10 years of schooling often answered symptom and diagnosis questions less positively. Parents with academic degrees, contrary to expectation, did not answer most precisely, this being especially true for the symptom questions. The association between symptom questions and clinical diagnosis was higher in West than in East Germany. We compared lifetime eczema symptoms and diagnosis with a point prevalence clinical diagnosis. In the absence of knowledge of how extraneous factors measured in this paper can affect diseases chronicity, it is difficult to say with certainty that such factors affect the validity of symptom and diagnosis questions on atopic eczema. Our study suggests that more studies are needed to examine the influence of social class, education and location on the validity of symptom questionnaires for atopic eczema. Until then, we recommend that information about such variables should be gathered routinely.

Variability of vigilance and ventilation: studies on the control of respiration during sleep

Ventilation is under metabolic as well as under behavioural control. This causes a complex interaction between states of 'vigilance' and respiration. This paper briefly summarizes sleep-related changes of respiration and presents an experimental study on the course of respiratory CO2-sensitivity during a whole night's sleep in ten healthy volunteers. The feedback control of breathing was challenged by continuous step changes of inspired CO2 every 7 min, resulting in 60, 3-step steady-state hypercapnic ventilatory responses (HCVR) per night in each subject. We analysed the variability of baseline ventilation and the effects of hypercapnia on ventilation with respect to sleep stages. There were only small differences in baseline PCO2 and ventilation between sleep stages, but a high variability of the slope of the CO2-response curves in the course of the night, ranging from 0.5 to 3.0 L min(-1) Torr(-1). The HCVR was significantly lower during REM sleep than during all stages of NREM sleep. Due to a compensatory left shift of the flattened CO2-response curves, however, ventilation at baseline CO2 as well as during slight hypercapnia varied much less than would be expected from the high variability of slopes. We conclude that the characteristics of the CO2-sensitive feedback control system of respiration, are highly variable during sleep, but due to offsetting effects, PCO2 and ventilation remain quite stable in the physiological range.

Self-similar core and oscillatory tails of a path-averaged chirped dispersion-managed optical pulse

We describe the breathing dynamics of the self-similar core and the oscillating tails of a dispersion-managed (DM) soliton. The path-averaged propagation equation governing the shape of the DM soliton in an arbitrary dispersion map is derived. The developed theory correctly predicts the locations of the dips in the tails of the DM soliton. A general solution of the propagation equation is presented in terms of chirped Gauss-Hermite orthogonal functions.

An essential role for a small synaptic vesicle-associated phosphatidylinositol 4-kinase in neurotransmitter release

Glutamate release from nerve terminals is the consequence of Ca2+-triggered fusion of small synaptic vesicles with the presynaptic plasma membrane. ATP dependence of neurotransmitter release has been suggested to be founded, in part, on phosphorylation steps preceding membrane fusion. Here we present evidence for an essential role of phosphatidylinositol phosphorylation in stimulated release of neurotransmitter glutamate from isolated nerve terminals (synaptosomes). Specifically, we show that a phosphatidylinositol 4-kinase (PtdIns 4-kinase) activity resides on nerve terminal-derived small synaptic vesicles (SSVs) and that inhibition of the PtdIns 4-kinase activity in intact synaptosomes leads to attenuation of the evoked release of glutamate. The attenuation of transmitter release is reversible and correlates with respective changes in intrasynaptosomal PtdIns 4-kinase activity. Because only the Ca2+-dependent release of glutamate is affected, regulation appears to be at the level of exocytosis. Taken together, our data imply a mandatory role for PtdIns 4-kinase and phosphoinositide products in the regulated exocytosis of SSV in mammalian nerve terminals.

[MORBUS: the Sentinel Practice Network. Report on a study in South Oldenbury]

There has been considerable public concern that emissions from intensive livestock farming may have hazardous effects on human health, particularly on the respiratory system. From October 1991 to September 1992, data on consultations of asthmatic children (up to 8 years) were obtained by a network of 25 GP and paediatric practices in South Oldenburg, a region with one of the highest livestock densities in Germany. Comparable data from a similar network of 75 practices in 3 adjacent regions (Brunswick, Hanover, Verden) with average livestock density served as a reference. In South Oldenberg, 2084 consultations of 542 asthmatic children were observed, with asthma being the reason for visit in 734 of the contacts (36%). The boy-girl ratio was 2.1:1 among index patients and 1.9:1 among consultations. Consultation rate was 25.2 contacts by asthmatic children per 1,000 total consultations of children up to 8 years in South Oldenburg, compared to 17.8 per 1,000 in Hanover, 15.7 per 1,000 in Brunswick and 13.6 per 1,000 in Verden. Consultations due to asthma scored 11.2/1,000 in South Oldenburg, 10.8/1,000 in Hanover, 7.2/1,000 in Brunswick and 6.5/1,000 in Verden. Asthmatic patients in South Oldenburg were younger (mean age 38 vs. 42 months) than those observed in the reference regions. There were no regional patterns in sex ratio, severity of asthma, respiratory allergies or atopic dermatitis. As this is an ecological study design, inferences concerning the cause of the observed regional differences can only be weak. We therefore propose a case-control study in order to obtain exposure and health data on an individual level.

Protein interactions implicated in neurotransmitter release

Biochemical evidence indicates that the exocytotic release of neurotransmitters involves both evolutionary conserved membrane proteins, the SNAREs, as well as ubiquitous cytosolic fusion proteins, NSF and SNAPs. We have analyzed the biochemical properties and the physiological effects of these proteins. Our data suggest models how NSF, SNAPs and SNAREs may function in neurotransmitter exocytosis.

Recombinant human follicle stimulating hormone for treatment of male idiopathic infertility: a randomized, double-blind, placebo-controlled, clinical trial

To examine the role of recombinant human follicle stimulating hormone (rhFSH) in male idiopathic infertility a randomized, double-blind, placebo-controlled study was performed. Of 211 patients screened, 67 were finally included. After two pre-examinations, patients were randomized and treated for 12 weeks, either with 150 IU rhFSH or with placebo. Examinations (physical examination, scrotal ultrasonography, semen analysis, hormone measurements, and in 31 patients electron microscopy (EM) of spermatozoa were performed 6 and 12 weeks after treatment initiation and 6 and 12 weeks after completion of treatment. Pregnancies were recorded for a further 3 months after the last examination. Of the 67 patients included in the study, 34 treated and 31 placebo patients could be analysed. In the treated group, FSH was elevated compared to baseline values (P < 0.001). At the end of treatment testicular volume in the treated group was increased compared to placebo (P < 0.05) and baseline (P < 0.001). Apart from an increase in sperm motility (P < 0.05) in the placebo group and in sperm DNA condensation (P < 0.001) in the treated group no significant changes were observed in semen parameters. Two spontaneous pregnancies in partners of men in the treated group and none in the placebo group occurred. However, two pregnancies occurred in partners of men in the placebo group induced by intrauterine insemination or intracytoplasmic sperm injection. In conclusion, at the chosen dose and duration, rhFSH did not lead to an improvement of conventional or EM sperm parameters nor to an increase in pregnancy rates. However, the increased testicular volume and sperm DNA condensation give reason for further investigations.

The heterotrimeric G protein Go2 regulates catecholamine uptake by secretory vesicles

Secretory vesicles store neurotransmitters that are released by exocytosis. Their membrane contains transporters responsible for transmitter loading that are driven by an electrochemical proton gradient across the vesicle membrane. We have now examined whether uptake of noradrenaline is regulated by heterotrimeric G proteins. In streptolysin O-permeabilized PC 12 cells, GTP-analogues and AlF4- inhibited noradrenaline uptake, an effect that was sensitive to treatment with pertussis toxin. Inhibition of uptake was prevented by Galphao-specific antibodies and mimicked by purified activated Galphao2. No effect was seen when Galphao2 in its inactive GDP-bound form or purified activated Galphao1, Galphai1 and Galphai2 were tested. Down-regulation of uptake remained unchanged when exocytosis was inhibited by the light chain of tetanus toxin. Vesicular acidification was not affected whereas binding of [3H]reserpine was reduced by GTPgammaS and Galphao2. These data suggest that the monoamine transporter rather than the vacuolar ATPase is affected. We conclude that catecholamine uptake is controlled by Galphao2, suggesting a novel function for heterotrimeric G proteins in the control of neurotransmitter storage.

[Reduction of inflammatory response after flap transfer by pretreatment with local heat shock]

In a rat model of free flap transfer local heat shock-priming is able to prevent ischemia/reperfusion-induced inflammatory response by expression of heat shock protein-32.

Disruption of syntaxin-mediated protein interactions blocks neurotransmitter secretion

The membrane protein syntaxin participates in several protein-protein interactions that have been implicated in neurotransmitter release. To probe the physiological importance of these interactions, we microinjected into the squid giant presynaptic terminal botulinum toxin C1, which cleaves syntaxin, and the H3 domain of syntaxin, which mediates binding to other proteins. Both reagents inhibited synaptic transmission yet did not affect the number or distribution of synaptic vesicles at the presynaptic active zone. Recombinant H3 domain inhibited the interactions between syntaxin and SNAP-25 that underlie the formation of stable SNARE complexes in vitro. These data support the notion that syntaxin-mediated SNARE complexes are necessary for docked synaptic vesicles to fuse.

Experiences with the severity scoring of atopic dermatitis in a population of German pre-school children

Severity scoring of atopic dermatitis (SCORAD) was introduced as a standard tool but has not been used in a population-based epidemiological study; the objective of the present study was to determine the practicability of this instrument in this setting. We assessed the distribution of the severity of atopic eczema in the community and investigated differences between east and west Germany. A factor analysis was then carried out to characterize the variables of this scoring system and to analyse possible relationships within them. A multicentre cross-sectional study was carried out in five east German and two west German locations in 1994; pre-school children (5-6 years old) were investigated and cases of atopic eczema identified by a dermatological examination. The SCORAD was used to determine the severity of atopic eczema and the results assessed using analysis of variance and principal component analysis (varimax rotation). In all, 1511 (76.2%) of the children originally contacted participated and 11.3% were diagnosed with atopic eczema at the time of examination. The median severity scores was 21.4 (interquartile range 13.5) and there was a tendency to higher scores in west Germany for the mean overall score, the intensity score and the extent. 'Erythema' (1.30 vs. 1.06; P = 0.006) and 'excoriation' (0.77 vs. 0.36; P = 0.002) were significantly more prominent in children with eczema from west Germany (adjusted for observer). Interobserver variabilities of the SCORAD parameters were calculated, adjusted for location and were in accordance with earlier findings. Principal component analysis identified three independent factors accounting for 54.1% of the total variance. A severity factor, characterized by 'extent', 'lichenification', 'excoriation' and 'pruritus', was separated from a factor with an acute eczema-type profile ('erythema', 'oedema', 'oozing') and a factor whose major characteristics were 'extent', 'dryness', and 'sleep loss'. We conclude that atopic eczema is frequent in pre-school children. The SCORAD proved to be readily applicable and useful in epidemiological studies, but further validation is needed.

[Limits of optimizing resource allocation by debiting the public health service]

Based on the Dornier consulting opinion on the public health service system of Berlin, the limits of optimising the resource allocation process are discussed with respect to austerity budgets. The discussion focuses firstly on problems of finding a consensus of opinion about public tasks and purposes in the German settings of pluralistic impact on health policy, and secondly on methodical, functional and practical limits. Methodical arguments are supported by a comparison of personal density with regard to the twelve largest cities of Western Germany, and supplemented by a factor analysis of sociodemographic characteristics in order to quantify the need of social work in an urban context. Functional and practical limits are demonstrated with respect to the realisation of the principle of subsidiary and concerning the practice of wholesale cut-downs of public health services budget.

Maternal smoking during pregnancy and lactation increases the risk for atopic eczema in the offspring

BACKGROUND

Maternal smoking during pregnancy has been shown to lead to immunologic changes in the offspring. However, little is known about the influence of this exposure on atopic manifestations.

OBJECTIVE

Our purpose was to investigate the influence of air pollutants on manifestations of atopy in preschool children.

METHODS

Unselected cohorts of a total of 678 5- to 6-year-old preschool children (350 boys, 328 girls) were investigated in areas with different degrees of air pollution in Bavaria. Data on the history of atopic diseases and other relevant factors were obtained by questionnaire. A skin-prick test was performed with common aeroallergens. Manifestation of atopy was defined as personal history of atopic disease or positive prick test to either grass pollen, house dust mite, or cat and analyzed multivariately.

RESULTS

Of all children, 38.9% exhibited at least one manifestation of atopy. Atopic eczema was reported in 7.9% to 15.5%, hayfever in 4.1% to 25.6%, and asthma in 3.0% to 8.1%. Of the mothers, 12.6% smoked during pregnancy or lactation or both. Analysis of the manifestation of atopy including sex, location, nitrogen oxide and sulfur dioxide exposure and maternal smoking as covariates revealed an influence of the maternal smoking during pregnancy/lactation. Of children whose mothers had smoked during pregnancy/lactation, 52.2% exhibited manifestations of atopy in contrast to 35.7% of children of nonsmoking mothers (p < 0.044). A history of atopic eczema was the only component of the variable "manifestation of atopy" that was significantly associated with maternal smoking during pregnancy and lactation. A causal interpretation of this finding, however, was not supported by a follow-up study.

CONCLUSION

Maternal smoking during pregnancy or lactation or both might play a role in the development of atopic eczema and should be avoided.

[Postnatal development of breathing control]

Respiratory movements already occur in the fetus together with low amplitude high frequency EEG. During birth external stimuli drive respiration, supported by the development of hypercapnia, hypoxia and acidosis. The thresholds of the chemosensitive systems adapt during the first hours and days of life (CO2 sensitivity) or weeks (hypoxic sensitivity). In 180 healthy infants between 5 days and 18 months of age we performed respiratory CO2-responses during NREM-sleep and studied the immediate response to inhalation of 60% oxygen (Dejours test) as well as in 8 children with congenital central alveolar hypoventilation syndrome (CCHS) and 15 infants who experienced an apparently life-threatening event (ALTE). Infants older than 2 weeks had a mean PCO2 of 40-42 mmHg, the slope of the CO2-response showed no age trend and was found in the range of adults with a 22-38% increase in ventilation per Torr increased PCO2. Preterm infants had a significant lower CO2-response (16 vs. 33%) until they reached their estimated normal birth date. In the ALTE group the CO2-response was suppressed to 17%. Children with CCHS did not respond to CO2 by increasing their ventilation, even after years. The response to hyperoxia as a measure of peripheral chemoreceptor activity decreased from a 31% initial inhibition of ventilation at 1 month to 20% at one year. Our results indicate that temporary or lasting reduction or lack of the respiratory CO2 sensitivity may cause apneic events or hypoventilation. Different slopes of CO2- and hyperoxic responses in very young infants compared to older ones favour the occurrence of oscillations in the control of breathing such as periodic breathing during sleep.

Study of the interactions of cadmium and zinc ions with cellular calcium homoeostasis using 19F-NMR spectroscopy

The effects of the heavy-metal ions Cd2+ and Zn2+ on the homoeostasis of intracellular free Ca2+ in E367 neuroblastoma cells were examined using 19F-NMR spectroscopy with the fluorinated chelator probe 1,2-bis-(2-amino-5-fluorophenoxy)ethane-N,N,N', N'-tetra-acetic acid (5F-BAPTA). First, the technique was used to quantify the uptake and intracellular free concentrations of the heavy metals after treatment of the cells with 20 microM CdCl2 or 100 microM ZnCl2. Secondly, metal-induced transients in intracellular free Ca2+ were recorded. Addition of 20 microM CdCl2, but not 100 microM ZnCl2, evoked a transient increase in Ca2+ from a resting level of 84 nM to approx. 190 nM within 15 min after addition of the metal. Zn2+ at 20 microM completely prevented the induction of a Ca2+ transient by Cd2+. Ca2+ was mobilized by Cd2+ from intracellular organelles, since depletion of these stores by thapsigargin abolished the effect of the toxic metal. Furthermore, 20 microM Cd2+ evoked a transient rise in cellular Ins(1,4,5)P3, reaching a maximum level within 5 min after addition of the metal. These results demonstrate that perturbation of the Ins(1,4,5)P3/Ca2+ messenger system is an early and discrete cellular effect of Cd2+.

Epidemiology of allergic diseases

The escalation of allergic diseases (hay fever, asthma, atopic eczema) over recent decades has been linked to an increase in environmental pollutants. The prevalence of hay fever is associated with genetic predisposition, and some reports show an association with urban areas, socioeconomic status, and combined high allergen and automobile exhaust exposure. In asthma, there is also some evidence for geographical variations in prevalence; exercise challenge tests prove positive more often in urban areas than in rural areas. Although genetic predisposition is the strongest single risk factor for atopic eczema, air pollutants may aggravate the condition by acting as unspecific irritants and immunomodulators, leading to increased immunoglobulin E expression. In a study of 678 pre-school children, the influence of maternal smoking habits on individual measures of atopy revealed a positive association between smoking during pregnancy/lactation, and a positive history of atopic eczema. An East-West German comparative study examining different types and levels of air pollution, i.e. sulphurous (industrial; East) and oxidising (urban; West), showed that the prevalence of atopic eczema was greatest in East Germany. When various direct and indirect parameters of air pollution exposure were measured, the greatest association with atopic eczema was found with NOx exposure (indoor use of gas without a cooker hood), and close proximity to roads with heavy traffic. The increased prevalence of atopic eczema cannot be explained by changes in study methodology over time, or conventional risk factors alone; environmental risk factors may be an important contributing factor.

Agonist-stimulated calcium transients in PC12 cells are affected differentially by cadmium and nickel

Rat pheochromocytoma (PC12) cells were loaded with the fluorescent indicator Fura-2 and the effects of cadmium and nickel on the mobilization of calcium elicited by bradykinin and external ATP were studied. Cadmium and nickel ions provoked a concentration-dependent decrease of the initial peak and/or the subsequent plateau phase of bradykinin-induced Ca2+ transients in a different manner: whereas cadmium (0.5-2.5 microM) diminished the calcium peak without modifying the sustained plateau, nickel (25-1000 microM) only slightly lowered the peak but markedly decreased the plateau phase. In the case of ATP-stimulated calcium transients, which are without a sustained plateau, both cadmium and nickel ions decreased the peak signal. Possible consequences are discussed in terms of a disturbance of hormone-stimulated cell activation by cadmium and nickel.

Effects of cadmium on cellular calcium and proto-oncogene expression

Effects of the carcinogenic metal cadmium on cellular calcium signalling and proto-oncogene expression were studied in mammalian cells. Cadmium ions interfered with bradykinin- and adenosinetriphosphate (ATP)-stimulated calcium transients in rat pheocromocytoma PC12 cells, but Cd2+ as such did not evoke intracellular Ca2+ spikes. At variance, cadmium ions caused a sustained elevation of intracellular free Ca2+ by inhibition of active calcium transport systems in various cell types. Problems of mutual interference of Ca2+ and Cd2+ analysis with the fluorescent probe Fura-2 could be overcome by the use of the fluorine 19 nuclear magnetic resonance (19F-NMR) probe acetoxymethyl ester of 1,2-bis(2-amino-5-fluorophenoxy)ethane-N,N,N'N'-tetraacetic acid (5F-BAPTA), which allows the measurement of free intracellular Ca2+, Cd2+ and other metal ions concurrently. Furthermore, the induction of the cellular protooncogenes c-fos and c-jun by Cd2+ was studied in PC12 cells. A dose of 0.5 microM Ca2+ sufficed to induce the c-Fos and c-Jun proteins within 30 min. These results support a model which suggests that cadmium stimulates cell proliferation by interference with intracellular calcium and induction of immediate early genes.

Engineered disulfide bonds in recombinant human interferon-gamma: the impact of the N-terminal helix A and the AB-loop on protein stability

Insertion sites for cysteines with optimal stereochemistry for the formation of unstrained disulfide bridges were identified in recombinant human interferon-gamma (rhu-IFN-gamma) by computer modelling. We have engineered two different disulfide cross-linked mutants, containing a pair of symmetry-related disulfide bonds, which stabilize the N-termini of both monomers of the homodimeric protein. Mutations E7C and S69C allow the formation of an intramonomer disulfide bond between helices A and D. In contrast, the A17C and H111C mutations lead to a covalent cross-link between both monomers. The AB-loop is linked to helix F. The fluorescence properties of native and disulfide cross-linked proteins were studied as a function of guanidine hydrochloride concentration. Melting temperatures (Tm) were calculated from the decrease in CD ellipticity at 220 nm. The induction of the antiviral effect was measured using A549 fibroblast cells infected with encephalomyocarditis virus. The ability to induce the expression of the HLA-DR antigen in Colo 205 cells was determined by fluorescence-activated cell scanning analysis. The stability of both mutants was strongly enhanced against temperature- and cosolvent-induced unfolding. The delta Tm of mutant IFN-gamma E7C/S69C was 15 degrees C. All measured biological activities of this mutant were equal to wild type. In the case of the other mutant IFN-gamma A17C/H111C, the delta Tm value was 25 degrees C. This mutation abolishes nearly the entire biological activity (< 1%) with no detectable changes of secondary structure in the CD spectrum. Our results illustrate the importance of the N-terminal helix A and the AB-loop for the unfolding pathway and thermodynamic stability of rhu-IFN-gamma.

Determination of the activities of the enzyme complexes of the electron transport chain in human fibroblasts

In order to improve the determination of the activities of the enzyme complexes of the electron transport chain (ETC) in fibroblasts, we characterized the isolation of mitochondria and measured enzyme activities in mitochondrial preparations from fibroblasts of control subjects and patients with suspected mitochondrial cytopathy. The isolation procedure yielded 54% of the citrate synthase activity in fibroblasts, with a 6-fold enrichment in this mitochondrial marker enzyme. The activities of the complexes of the ETC were linear with time and with the mitochondrial protein concentration used. The coefficients of variation for the enzyme activities determined were in the range of 10% in mitochondria from identical fibroblast cultures and between 30 and 70% in mitochondria from different fibroblast cultures of the same or of different patients. Decreased activities of one or more enzyme complexes (defined as an activity below the 95% confidence limit of control values) were found in 15 of 22 patients investigated. When compared with activities obtained in liver or skeletal muscle obtained at autopsy, the results were identical in three but different in two patients. The studies show that the activities of the enzyme complexes of the ETC can be determined reliably and reproducibly in mitochondria isolated from fibroblasts and that the results obtained are potentially useful for the diagnosis of mitochondrial cytopathies in patients with suggestive symptoms and signs.

Modelling hybridoma cell growth and metabolism--a comparison of selected models and data

Unstructured models for cell growth (cell specific growth and death rate) and metabolism (cell specific substrate uptake and metabolite production rates) of hybridoma cell lines were compared with special respect to significance, analytical error and range of validity. The diversity of the unstructured models cited reveals their mostly descriptive character compared to structured models. Bearing in mind this limited knowledge, empirical models can still serve as a valuable tool for process design. For understanding of the cell metabolism itself they might have been overemphasized in the past. For proper model design, care has to be taken to cover the whole range of process conditions. In particular if a process is to be run at very low substrate and high metabolite concentrations, chemostat cultures which have mostly been used for the model formulations, are not sufficient and have to be completed by, for example, fed-batch cultures.

Atopic eczema and other manifestations of atopy: results of a study in East and West Germany

Within an environmental health study, dermatologic examination of 1273 pre-school-age children (5-7 years old) was carried out in selected areas of East (n = 287) and West (n = 987) Germany in spring 1991. On the basis of comparable genetic background, the influence of a different exposure to air pollutants on the manifestation of atopic diseases was investigated. Halle an der Saale (East Germany) and Duisburg (North/South) as well as Essen (West Germany) were chosen as polluted study areas, whereas the countryside town of Borken (West Germany) served as a control region. Outdoor pollution with particles and SO2 was significantly higher in Halle an der Saale. Of the total study group, 12.9% suffered from atopic eczema at the time of examination. The prevalence was highest in East Germany (17.5%; adjusted odds ratio [OR] 1.39, confidence intervals [GI] 0.77-2.52, compared to Borken). The reported frequencies of hay fever and asthma in the total study population were 2% and 1.3%, respectively, without significant differences between study sites. Some 34.7% of the children showed at least one positive skin prick test reaction; significantly (P < 0.001) higher sensitization rates were obtained in western regions (Essen, Duisburg-South) than in the control region (Borken) and East Germany. Multivariate analysis of the prevalence of atopic eczema showed associations with parental predisposition (OR 1.52, CI 1.03-2.25), sex (for boys, OR 0.63, CI 0.43-0.92), location (Duisburg-South vs Borken OR 0.52, CI 0.30-0.96), month of investigation (May vs April, and March vs February OR 0.55, CI 0.37-0.81), contact with rabbits (for girls, OR 2.90, CI 1.36-6.19), animal fur in bedrooms (2.17, 1.01-4.67), indoor use of gas without hood (1.68, 1.11-2.56), and distance of homes from a busy road (< 50 m 1.71, 1.07-2.73). Nonsignificant associations were observed for history of helminthic infections (OR 1.61, CI 0.98-2.64) and high parental education level (OR 1.83, CI 0.83-4.02). In East and West Germany, atopic eczema seems to follow a course different from that of respiratory allergic diseases and specific sensitization, a fact which underlines the need for a differentiated analysis.

Three extremely thermostable proteins from Sulfolobus and a reappraisal of the 'traffic rules'

Three cytosolic enzymes from the extremely thermoacidophilic archaeon Sulfolobus acidocaldarius (DSM 639) have been investigated: adenylate kinase, pyrophosphatase and superoxide dismutase. The latter was isolated from S. acidocaldarius cells, the others were heterologically overproduced in Escherichia coli. Long-term thermostability, flexibility, catalytic activity, and thermal denaturation were investigated by biochemical and physical methods. Superoxide dismutase is hyperthermostable over several days. The other enzymes have Tm values between 87 degrees C - 98 degrees C depending on conditions and reveal long-term stability in the range of hours. On the basis of sequence alignments, core structures were defined and compared to mesophilic homologues selected by growth temperature of organisms from 25 degrees C to 88 degrees C. The data set confirms none of the simple sequence based 'traffic rules' previously proposed by others. Some aspects of thermostability based on molecular modeling studies are discussed which remain to be proved by the 3D structures. All three enzymes could be crystallized.

IgE antibodies to Hymenoptera venoms in the serum are common in the general population and are related to indications of atopy

Determination of Hymenoptera venom (HV)-specific serum IgE antibodies is a useful diagnostic method in patients with systemic anaphylactic reaction (SAR) to Hymenoptera stings. In a general population cohort, we determined the prevalence of SAR and HV-specific IgE antibodies and assessed parameters associated with the latter. A total of 277 voluntarily participating inhabitants of rural Bavaria (Germany) (232 adults, mean age 38.0 years; 45 children, mean age 8.4 years) were investigated for a history of atopic disease or SAR to insect stings; in 258 of these, total IgE and specific IgE antibodies to HV (Apis mellifera, Vespula vulgaris/germanica) and four common aeroallergens (birch pollen, grass pollen, house-dust mite, and cat dander) in the serum were determined. Nine (3.3%) subjects reported SAR to insect stings. In 27.1% of the sera, specific IgE antibodies to HV were found, to bee venom in 24.8%, and to wasp venom in 8.5% (P < 0.0001). Of those exhibiting HV-specific IgE, 7.1% reported SAR to insect stings. A personal history of atopic disease (hay fever, asthma, or atopic eczema) was present in 16.7%, specific IgE to common aeroallergens was found in 32.6%, and total IgE > 100 kU/l was found in 22.5%. Specific serum IgE to HV was significantly associated with male sex (female vs. male, OR = 0.47; CI 0.25-0.86), young age (children vs. adults, OR = 2.80; CI 1.25-6.28), a history of SAR to insect stings (OR = 4.16; CI 1.15-15.03), total sIgE > 100 kU/l (OR = 3.88; CI 1.98-7.60), and specific IgE antibodies to three of the four aeroallergens (grass pollen, OR = 7.24 CI 3.66-14.38; birch pollen, OR = 3.67 CI 1.54-8.81; and house-dust mite, OR = 4.61 CI 2.08-10.32). It is concluded that immunologic sensitization to HV is common in the general population and is associated with atopy-related humoral IgE hyperresponsiveness.

Chromaffin granule-associated phosphatidylinositol 4-kinase activity is required for stimulated secretion

Permeabilized bovine adrenal chromaffin cells have been used to characterize the MgATP requirement of processes preceding exocytosis. Incubation of primary cultures with the membrane-permeable phenylarsine oxide (PAO) at 20 microM inhibited the phosphorylation of phosphatidylinositol (PtdIns) and completely blocked secretion. This block could be reversed by addition of 2,3-dimercaptopropanol to the permeabilized cells. Simultaneous addition of [gamma32P]ATP and 2,3-dimercaptopropanol permitted a comparison between recovery of secretion and phosphorylation of intracellular components. Recovery of secretion closely correlated with phosphorylation of PtdIns and PtdIns4P. Subcellular fractionation of permeabilized cells after recovery of secretion revealed that the majority of newly phosphorylated PtdIns4P was localized on the chromaffin granules. In accordance with these results, PtdIns 4-kinase activity was found in protein extracts of permeabilized cells as well as associated with purified chromaffin granules, sensitive in both cases to PAO. Additionally, PtdIns 4-kinase activity in these two assays was inhibited by quercetin. In permeabilized cells, quercetin decreased the levels of labeled PtdIns4P and Ptdlns(4,5)P2 and inhibited secretion. Our data suggest that a chromaffin granule-associated PtdIns 4-kinase acts in the priming of exocytosis.

[Sleep and breathing disorders in patients with brain stem lesions]

Most information about the structures within the brain stem that modulate respiration and sleep are gathered from animal experiments. Therefore we examined 10 patients several weeks after an infarction of the brain stem by means of polysomnography and tested the chemosensitive drives of respiration. None of these patients complained about symptoms of sleep disordered breathing. In each case polysomnographic measurements and ventilatory response curves revealed pathologic findings. The respiratory response to CO2 was diminished or completely abolished in each patient. In some cases hypoventilation or disturbances of the respiratory rhythmicity could be seen. In several cases missing REM sleep, sleep fragmentation or the reduction of slow wave sleep were observed. The study indicates that on the base of results from animal research the comparison of morphological and pathophysiological data is helpful to gain a better understanding on the coupling of the respiratory system with sleep at the brain stem level as well as on the pathomechanism of sleep related breathing disorder.

[Computer-assisted analysis of sleep stages using the laboratory software package "Spike 2"]

We used a laboratory software package for data capture and data analysis (Spike 2, CED) to develop a computerised sleep staging. The modular software is programmed to extract the following data: power spectral density in the alpha and delta frequency bands with fast Fourier Transformation, K-complexes using pattern recognition on the basis of signal amplitude and zero level crossings, sleep spindles using auto-correlation of the EEG signal, rapid eye movements with pattern recognition of the bipolar EOG signal using amplitude and time differences, and muscle tone from the rectified and integrated submental EMG signal. These results are displayed together with the raw signals of EEG, EOG, and chin EMG on a user-defined time scale. Thus visual scoring of sleep stages is easter. Furthermore a decision table, containing the sequence and weighting factors for the extracted parameters, serves to perform an automated sleep scoring.

Gastric emptying and release of incretin hormones after glucose ingestion in humans

This study investigated in eight healthy male volunteers (a) the gastric emptying pattern of 50 and 100 grams of glucose; (b) its relation to the phase of interdigestive motility (phase I or II) existing when glucose was ingested; and (c) the interplay between gastric emptying or duodenal perfusion of glucose (1.1 and 2.2 kcal/min; identical total glucose loads as orally given) and release of glucose-dependent insulinotropic peptide (GIP), glucagon-like peptide-1(7-36)amide (GLP-1), C-peptide, insulin, and plasma glucose. The phase of interdigestive motility existing at the time of glucose ingestion did not affect gastric emptying or any metabolic parameter. Gastric emptying of glucose displayed a power exponential pattern with a short initial lag period. Duodenal delivery of glucose was not constant but exponentially declined over time. Increasing the glucose load reduced the rate of gastric emptying by 27.5% (P < 0.05) but increased the fractional duodenal delivery of glucose. Both glucose loads induced a fed motor pattern which was terminated by an antral phase III when approximately 95% of the meal had emptied. Plasma GLP-1 rose from basal levels of approximately 1 pmol/liter of peaks of 3.2 +/- 0.6 pmol/liter with 50 grams of glucose and of 7.2 +/- 1.6 pmol/liter with 100 grams of glucose. These peaks occurred 20 min after glucose intake irrespective of the load. A duodenal delivery of glucose exceeding 1.4 kcal/min was required to maintain GLP-1 release in contrast to ongoing GIP release with negligibly low emptying of glucose. Oral administration of glucose yielded higher GLP-1 and insulin releases but an equal GIP release compared with the isocaloric duodenal perfusion. We conclude that (a) gastric emptying of glucose displays a power exponential pattern with duodenal delivery exponentially declining over time and (b) a threshold rate of gastric emptying of glucose must be exceeded to release GLP-1, whereas GIP release is not controlled by gastric emptying.

[Continuous ambulatory monitoring in quality control of home therapy of congenital central hypoventilation syndrome (CCHS)]

4 children with congenital central hypoventilation syndrome (CCHS) now aged 6 to 9 years were studied for 1 to 8 years. In all patients CO2-response is missing, hypoxic drive is maintained. All patients required mechanical ventilation after birth. 1 patient is supported by controlled oxygen therapy during sleep since 9 months of age. 2 patients are IPPV-ventilated during sleep. 1 patient is pressure control ventilated with an oro-nasal mask since 6 years of age. All children showed phases of hypo- and hyperventilation (max. pCO2 107 mm Hg) depending on vigilance with respiratory acidosis in awake state and during sleep. These findings required ambulatory monitoring of home-therapy by a professional guard and continuous recording of pCO2 and pulseoximetry. These longtime data (max. pCO2 72 mm Hg) show that ambulatory monitoring and control of therapy is able to avoid extreme variation of blood gases and to stabilize acid-base regulation during sleeptime in patients with CCHS.

Localization of chemosensitive structures in the isolated brainstem of adult guinea-pig

1. Central respiratory chemosensitivity has been intensively examined but some questions remain unsolved; namely, what is the nature of the stimulus (fixed acid and/or CO2) and where is the site of brainstem chemosensitivity (near the ventral medullary surface or structures deeper within the brainstem)? To examine these questions, we used the in vitro isolated brainstem of adult guinea-pig perfused independently through the basilar artery and the bath. 2. Respiratory motor output was recorded with a suction electrode from cranial hypoglossal (XII) roots. Changes in pH and CO2 in the Krebs perfusate were made by changing either the bicarbonate concentration or the PCO2 saturating the Krebs solution. 3. Changes in basilar artery perfusate consisting of (i) an acidifying increase in PCO2 (hypercapnic acidic Krebs solution), (ii) an increase in PCO2 with no change in pH (hypercapnic Krebs solution), or (iii) a decrease in pH with no change in PCO2 (acidic Krebs solution) evoked increases in respiratory frequency and a concomitant decrease in inspiratory burst amplitude. 4. Bath superfusion with hypercapnic acidic Krebs solution increased the inspiratory burst amplitude with no effect on respiratory burst frequency. 5. Bath superfusion with hypercapnic non-acidic Krebs solution increased the inspiratory burst amplitude and decreased the respiratory frequency, while normocapnic acidic Krebs solution increased the respiratory frequency with no change in burst amplitude. 6. These results show that respiratory responses to changes in CO2 and pH depend upon the sites of action. While a CO2 increase or a pH decrease affected the respiratory frequency in the deep brainstem structures (perfused through the basilar artery), CO2 respiratory chemosensitivity at the ventral surface could be differentiated from the hydrogen ion chemosensitivity. This suggests that different mechanisms mediated respiratory responses when deep versus superficial brainstem structures were stimulated.

Somatodendritic localization and hyperphosphorylation of tau protein in transgenic mice expressing the longest human brain tau isoform

Microtubule-associated protein tau is the major constituent of the paired helical filament, the main fibrous component of the neurofibrillary lesions of Alzheimer's disease. Tau is an axonal phosphoprotein in normal adult brain. In Alzheimer's disease brain tau is hyperphosphorylated and is found not only in axons, but also in cell bodies and dendrites of affected nerve cells. We report the production and analysis of transgenic mice that express the longest human brain tau isoform under the control of the human Thy-1 promoter. As in Alzheimer's disease, transgenic human tau protein was present in nerve cell bodies, axons and dendrites; moreover, it was phosphorylated at sites that are hyperphosphorylated in paired helical filaments. We conclude that transgenic human tau protein showed pre-tangle changes similar to those that precede the full neurofibrillary pathology in Alzheimer's disease.