Beta subunit heterogeneity in neuronal L-type Ca2+ channels

Heterologous expression studies have shown that the activity of voltage-gated Ca2+ channels is regulated by their beta subunits in a beta subunit isoform-specific manner. In this study we therefore investigated if one or several beta subunit isoforms associate with L-type Ca2+ channels in different regions of mammalian brain. All four beta subunit isoforms (beta1b, beta2, beta3, and beta4) are expressed in cerebral cortex as shown in immunoblots. Immunoprecipitation of (+)-[3H]isradipine-labeled L-type channels revealed that the majority of beta subunit-associated L-type channels was associated with beta3 (42 +/- 8%) and beta4 (42 +/- 7%) subunits, whereas beta1b and beta2 were present in a smaller fraction of channel complexes. beta3 and beta4 were also the major L-type channel beta subunits in hippocampus. In cerebellum beta1b, beta2, and beta3 but not beta4 subunits were expressed at lower levels than in cortex. Accordingly, beta4 was the most prominent beta subunit in cerebellar L-type channels. This beta subunit composition was very similar to the one determined for 125I-omega-conotoxin-GVIA-labeled N-type and 125I-omega-conotoxin-MVIIC-labeled P/Q-type channel complexes in cerebral cortex and cerebellum. Our data show that all four beta subunit isoforms associate with L-type Ca2+ channels in mammalian brain. This beta subunit heterogeneity may play an important role for the fine tuning of L-type channel function and modulation in neurons.

DNA single strand breakage, DNA adducts, and sister chromatid exchange in lymphocytes and phenanthrene and pyrene metabolites in urine of coke oven workers

OBJECTIVES

To investigate the specificity of biological monitoring variables (excretion of phenanthrene and pyrene metabolites in urine) and the usefulness of some biomarkers of effect (alkaline filter elution, 32P postlabelling assay, measurement of sister chromatid exchange) in workers exposed to polycyclic aromatic hydrocarbons (PAHs).

METHODS

29 coke oven workers and a standardised control group were investigated for frequencies of DNA single strand breakage, DNA protein cross links (alkaline filter elution assay), sister chromatid exchange, and DNA adducts (32P postlabelling assay) in lymphocytes. Phenanthrene and pyrene metabolites were measured in 24 hour urine samples. 19 different PAHs (including benzo(a)pyrene, pyrene, and phenanthrene) were measured at the workplace by personal air monitoring. The GSTT1 activity in erythrocytes and lymphocyte subpopulations in blood was also measured.

RESULTS

Concentrations of phenanthrene, pyrene, and benzo(a)pyrene in air correlated well with the concentration of total PAHs in air; they could be used for comparisons of different workplaces if the emission compositions were known. The measurement of phenanthrene metabolites in urine proved to be a better biological monitoring variable than the measurement of 1-hydroxypyrene. Significantly more DNA strand breaks in lymphocytes of coke oven workers were found (alkaline filter elution assay); the DNA adduct rate was not significantly increased in workers, but correlated with exposure to PAHs in a semiquantitative manner. The number of sister chromatid exchanges was lower in coke oven workers but this was not significant; thus counting sister chromatid exchanges was not a good variable for biomonitoring of coke oven workers. Also, indications for immunotoxic influences (changes in lymphocyte subpopulations) were found.

CONCLUSIONS

The measurement of phenanthrene metabolites in urine seems to be a better biological monitoring variable for exposure to PAHs than measurement of hydroxypyrene. The alkaline filter elution assay proved to be the most sensitive biomarker for genotoxic damage, whereas the postlabelling assay was the only one with some specificity for DNA alterations caused by known compounds.

Gangliosides GM1, GM2 and GM3 inhibit the platelet-derived growth factor-induced signalling transduction pathway in vascular smooth muscle cells by different mechanisms

Gangliosides appear to regulate proliferation of different cell types. In the present study, we investigated the effects of gangliosides GM1, GM2 and GM3 on platelet-derived growth factor (PDGF)-induced vascular smooth muscle cell (VSMC) growth. In addition, we examined the effects of gangliosides on the PDGF-BB-dependent signalling transduction pathway in rat aortic VSMC. GM2 and GM1 inhibit the PDGF-BB-dependent receptor tyrosine autophosphorylation, stimulation of the PLC-gamma 1, increase of inositol-1,4,5-trisphosphate (InsP3), elevation in cytosolic free Ca2+ ([Ca2+]i), expression of the immediate early growth response gene c-fos and cell proliferation with the following rank order of potency GM2 > GM1. Although GM3 did not influence the PDGF-BB-dependent receptor autophosphorylation and PLC-gamma 1 activation, it effectively inhibited the PDGF-BB-dependent InsP3 formation, [Ca2+]i and cell growth. Binding studies with 125I-PDGF-BB on VSMC in the presence and absence of 10 to 50 microM of each ganglioside revealed that GM1 and GM2 effectively inhibited the specific binding of PDGF-BB with an IC50 value of 20 microM for GM2 and 30 microM for GM1. GM3 had no significant effect on the specific 125I-PDGF-BB binding. These observations suggest that GM1 and GM2 may interact with PDGF-BB or its receptor resulting in a prevention of its binding. GM3 was able to suppress the PDGF-BB-dependent increase of InsP3 and [Ca2+]i downstream of the PDGF-BB-dependent receptor autophosphorylation and PLC-gamma 1 activity.

Identification of benz(othi)azepine-binding regions within L-type calcium channel alpha1 subunits

To identify the binding domain for diltiazem-like Ca2+ antagonists on L-type Ca2+ channel alpha1 subunits we synthesized the benzazepine [3H]benziazem as a novel photoaffinity probe. [3H]Benziazem reversibly labeled the benzothiazepine (BTZ)-binding domain of partially purified skeletal muscle Ca2+ channels with high affinity (Kd = 12 nM) and photoincorporated into its binding domain with high yield (>66%). Antibody mapping of proteolytic labeled fragments revealed specific labeling of regions associated with transmembrane segments S6 in repeats III and IV. More than 50% of the labeling was found in the tryptic fragment alanine 1023-lysine 1077 containing IIIS6 together with extracellular and intracellular amino acid residues. The remaining labeling was identified in a second site comprising segment S6 in repeat IV and adjacent residues. Unlike for dihydropyridines, no labeling was observed in the connecting IIIS5-IIIS6 linker. The [3H]benziazem photolabeled regions must be in close contact to the drug molecule when bound to the channel. We propose that the determinants for high affinity BTZ binding are located within or in close proximity to segments IIIS6 and/or IVS6. Therefore the binding domain for BTZs, like for the other main classes of Ca2+ antagonists, must be located in close proximity to pore-forming regions of the channel.

32P-postlabeling analysis of DNA adducts in different populations

Blood samples were obtained from different populations exposed occupationally or by lifestyle habits to polycyclic aromatic hydrocarbons (PAH). DNA adducts were determined by 32P-postlabeling assay either in white blood cells (WBC) or lymphocytes. The level of DNA adducts ranged from 1.5 per 10(9) nucleotides in one of the control groups up to 7.1 per 10(9) nucleotides in one group of PAH-exposed workers. Comparison of the adduct thin layer chromatography (TLC) profiles revealed individual variation in both pattern and level of DNA adducts. Significant differences of adduct levels were detected between one group of PAH-exposed coke-oven workers and the corresponding control group. Only a weak influence of the smoking habits on the amount of adducts was detectable in occupationally exposed or unexposed individuals.

Sister chromatid exchange frequencies in lymphocytes of oral cancer patients seem to be influenced by drinking habits

Sister chromatid exchange (SCE) values were determined in the lymphocytes of 24 oral cancer patients before therapy and in the lymphocytes of 24 control persons standardized with respect to sex, age and smoking habits. Oral cancer patients showed significantly elevated SCE values (mean 7.82 versus 6.42). In both groups the highest SCE values were found in the subgroups with the highest alcohol consumption. A significant correlation between SCE and gamma-glutamyltranspeptidase (GGT) values by Spearman correlation analysis was detected in the combined group (cancer patients and control persons) (n = 32, r = 0.40, P = 0.023). The SCE values in the oral cancer patients were weakly correlated (Pearson) to DNA adduct levels (n = 22, r = 0.39, P = 0.068) and DNA single-strand breakage frequencies (n = 12, r = 0.56, P = 0.054) in lymphocytes. The correlation (Pearson) between SCE values and DNA strand breakage values in lymphocytes was significant (n = 10, r = 0.67, P = 0.036) in smoking cancer patients. The increase of SCE values with respect to alcohol drinking habits underlines epidemiologic findings that alcohol is an important co-carcinogen in many cancers, especially in oral cancers. Because of the influences on SCE and adduct levels in lymphocytes, alcohol drinking habits should be controlled as broadly as possible in biomarker studies.

DNA strand breakage and DNA adducts in lymphocytes of oral cancer patients

In lymphocytes of 12 oral cancer patients (and two control groups) the frequencies of DNA single-strand breaks and DNA-protein cross-linking were determined by alkaline filter elution. We found elevated DNA elution rates, which must be interpreted as an increased strand breakage frequency. There were significant correlations between the DNA strand breakage frequency and smoking habits. Using the 32P-postlabelling assay we determined the DNA adduct level in lymphocytes of 23 oral cancer patients (and two control groups). No significant influence of smoking habit on the DNA adduct level could be detected. There was a significant correlation between the DNA adduct level and the gamma-glutamyltranspeptidase (GGT) value, suggesting systemic influences of alcohol drinking habits on the adduct level.

[Polychlorinated biphenyls (PCBs) and reproduction disturbances]

A review of the impact of chlorinated biphenyls (PCBs) on reproduction is presented. PCBs are able to pass the placenta; accumulation in offspring is mainly achieved by breast feeding. Disturbances of fertility and embryotoxicity were detected in animals; teratogenicity without maternal toxicity was only observed in mice. In animal experiments disturbances of fetal and postnatal development were detected as well as in human studies. Neurotoxicity was observed even at low-level exposures in monkeys, which are most comparable to humans because of the development of the same clinical symptoms. Technical PCBs which are dominating in occupational and environmental exposure until now must be judged as toxic for reproduction: dermal exposure (especially in accidents) should be considered as an important route of exposure beside inhalation. Work to list possible PCB exposure risks and to develop ways to reduce these risks are necessary now.

Activity testing of alveolar macrophages and changes in surfactant phospholipids after irradiation in bronchoalveolar lavage: experimental and clinical data

This study presents results of bronchoalveolar lavage (BAL) after irradiation to the lungs in mice as well as clinical data. The number of BAL cells, mainly macrophages, lymphocytes, and granulocytes, changed in a time-dependent manner. The phagocytic activity of the macrophages measured as the phagocytosis of microbeads and measured as the esterase activity also showed a strong time-dependent increase during the acute phase up to 21 days after irradiation. The contents of surfactant phospholipids (SF) and sphingomyelin (SPH; as a parameter for cell death) were quantified by HPLC. Both were significantly changed between day 2 and 21 after irradiation. Three BALs of a patient with idiopathic interstitial pneumonitis, who had received an allogenic bone marrow graft after total body irradiation with 10 Gy, showed similar effects in the cellular and surfactant parameters. These data indicate that there are positive interactions between the number of different BAL cells, macrophage activity, and SF and SPH content in the preclinical model of the mouse as well as in the clinical situation after lung irradiation.

Radiation-induced changes in lung tissue and development of fibrosis determined by quantitative morphometric methods

This study presents results of morphometric investigations of mouse lungs after single irradiation. An automatic image analyser was used to monitor pathological changes in morphological structure, especially the size and distribution of collagen fibres, the thickness of the septa and the diameters of alveoli in the lung. Radiation-induced changes in the area of alveoli and septa as well as collagen content were seen 11 weeks after irradiation. A dose-dependent increase in tissue and decrease in alveolar surface as well as a quantifiable increase in radiation oedema were seen. The septa were thickened and the total collagen content increased in a dose-dependent manner. The morphometric methods used here are suitable for determining changes in lung structure, particularly those in collagen content in the early phase of a pathological response after thorax or total body irradiation for conditioning in bone marrow transplantation.

Sonography of neck masses in children

The sonograms and medical records of 49 patients were reviewed to determine if there is a characteristic sonographic appearance for certain neck masses. Neck masses included: inflammatory masses (12), noninflammatory masses (23), and thyroid masses (14). Four entities including thyroglossal duct cyst, fibromatosis colli, cystic hygroma, and multiple lymphadenopathy showed characteristic sonographic appearance. Thyroglossal duct cysts were seen as midline or slightly off midline cystic masses. A sinus tract extending superiorly was nicely demonstrated in one patient. The mass in fibromatosis colli (neonatal torticollis) appeared as a well defined mass clearly within the sternocleidomastoid muscle, uniformly echogenic, but less echogenic than the normal surrounding muscle, without good through-transmission. A cystic or primarily cystic mass with linear septations was the characteristic finding of the cystic hygroma. Multiple lymphadenopathy demonstrated multiple discrete, oval, relatively hypoechoic masses along the cervical lymphatic chain. The sonographic appearance of inflammatory masses was variable, being either inhomogeneously echogenic or of mixed echogenicity. Hemangiomas were either echogenic with cystic vascular spaces or linear septations or relatively homogeneously echogenic. Intrinsic thyroid masses could be distinguished from extrinsic masses in most cases. The demonstration of calcification in a mass was useful in narrowing the differential diagnosis. Although it is not a specific finding, the presence of calcification highly suggests a neoplastic lesion, particularly neuroblastoma or teratoma. Not only can the location, extent, and internal characteristics of a mass be determined, but in certain entities, the sonographic appearance is characteristic and an accurate diagnosis can be made.

Comparison of cardiovascular response to combined static-dynamic effort, postprandial dynamic effort and dynamic effort alone in patients with chronic ischemic heart disease

The cardiovascular responses to combined static-dynamic effort, postprandial dynamic effort and dynamic effort alone were evaluated by upright bicycle ergometry during equilibrium-gated blood pool scintigraphy in 24 men, mean age 59 +/- 8 years, with chronic ischemic heart disease. Combined static-dynamic effort and the postprandial state elicited a peak cardiovascular response similar to that of dynamic effort alone; work load 643 +/- 156 and 638 +/- 161 vs 650 +/- 153 kg-m/min, respectively; heart rate 147 +/- 14 and 145 +/- 14 vs 143 +/- 17 beats/min; systolic pressure 195 +/- 26 and 200 +/- 25 vs 197 +/- 25 mm Hg; and rate-pressure product 286 +/- 48 and 292 +/- 55 vs 282 +/- 52. Heart rate, intraarterial systolic and diastolic pressures, rate-pressure product and ejection fraction were similar for the three test conditions at the onset of ischemia and at peak effort. The prevalence and extent of exercise-induced ischemic left ventricular dysfunction, ST-segment depression, angina pectoris and ventricular ectopic activity were also similar during the three test conditions. Direct and indirect measurements of systolic and diastolic blood pressure were highly correlated. The onset of ischemic ST-segment depression and angina pectoris correlated as strongly with heart rate alone as with the rate-pressure product during all three test conditions. The cardiovascular response to combined static-dynamic effort and to postprandial dynamic effort becomes more similar to that of dynamic effort alone as dynamic effort reaches a symptom limit. If significant ischemic and arrhythmic abnormalities are absent during symptom-limited dynamic exercise testing, they are unlikely to appear during combined static-dynamic or postprandial dynamic effort. This simplifies, the task of formulating guidelines for physical effort in patients with chronic ischemic heart disease, especially in providing "clearance" to perform avocational and vocational tasks involving combined static-dynamic and postprandial dynamic effort.

[Use of cryocauterization in benign processes in the uterine cervix]

The authors report on their experience with the application of low temperatures in benign alterations of the cervix. Technical details of the process are described, as well as the clinical progress after the application of cryogenic devices. The results of cryotherapy in a series of 96 cases are presented. Special stress is given to the cosmetic effect of the method applied to the cervix deformed through the laceration of the orifice.