Subcellular localisation, protein interactions, and RNA binding of Potato mop-top virus triple gene block proteins

Subcellular localisation, protein interactions, and RNA binding of the triple gene block proteins (TGBp) of Potato mop-top virus (PMTV) were studied. The 13-kDa (TGBp2) and 21-kDa (TGBp3) proteins with or without green fluorescent protein fused to their N-terminus, and the 51-kDa protein (TGBp1) were expressed individually from a recombinant Tobacco mosaic virus (TMV) vector. Fluorescent images and Western immunoblotting experiments of recombinant TMV-infected Nicotiana benthamiana cells suggested that TGBp2 and TGBp3 were associated with cellular endomembranes and that TGBp3 was associated with the cell wall, possibly located close to plasmodesmata. In Western blots, TGBp1 was detected in fractions containing the cell wall and those enriched for organelles and membranous structures. Self-interactions were demonstrated with all three proteins in yeast two-hybrid experiments, and a heterologous interaction was found between TGBp2 and TGBp3. No additional heterologous interactions were discovered between the different TGBp and none were detected in an in vitro binding assay. TGBp1 and TGBp2 but not TGBp3 were shown to bind ssRNA in a sequence nonspecific manner. The results support the model where TGBp2 and TGBp3 facilitate delivery and localisation of the ribonucleoprotein complex to the plasmodesmata. However, the process is facilitated by RNA-protein rather than protein:protein interactions between the TGBp1 in complex with viral RNA and membrane-localised TGBp2.

X-ray microprobe analysis of epithelial calcium transport

The sternal epithelium of Porcellio scaber was used as a novel model to study the subcellular elemental distribution in control and Ca(2+)-transporting stages in situ. The anterior sternal epithelium (ASE) is specialized for transport of cuticular Ca to sternal CaCO(3) deposits during premolt, and from these deposits during intramolt. The less specialized posterior sternal epithelium transports Ca(2+) to and from the cuticle. In the ASE cells basal [Na], [Cl], and [Mg] are higher than in the apical side. The basal [Na] increases from 105 to 173 mmol/kg dry mass between control and Ca(2+)-transporting stages, accompanied by a decrease in [Cl] and [K]. The [Mg] increases, suggesting transepithelial Mg(2+)-transport. Cytosolic [Ca] varied insignificantly between 4.5 and 5.7 mmol/kg dry mass, however, the number of Ca hot-spots with concentrations between 15 and 50 mmol/kg dry mass increased during transport. Mitochondrial [Ca] decreased in the ASE from 3.3 in the control to 1.0 in the late premolt and to 2.0 mmol/kg dry mass in the intramolt stage. The results suggest Na(+)-dependent mechanisms for transcellular Ca(2+)-transport and the presence of Ca(2+)-binding proteins. Organelles, probably the smooth endoplasmic reticulum, sequester Ca(2+) during intracellular Ca(2+)-transport. A role of mitochondria as a storage site for cuticular Ca is excluded.

German national case collection of familial pancreatic cancer - clinical-genetic analysis of the first 21 families

BACKGROUND

The observation of a familial accumulation of ductal pancreatic adenocarcinoma (PC) and the increased risk for PC in certain hereditary tumor syndromes point to a genetic predisposition for PC. In order to evaluate the characteristics of familial PC, a German national case collection for familial pancreas cancer (FaPaCa) was established.

PATIENTS AND METHODS

In FaPaCa, families of patients with PC are being collected, who have at least 1 first-degree relative with PC or with malignant melanoma. Histopathologic verification of tumor diagnoses, acquisition of clinical data, and full genetic counselling are prerequisites for the enrollment of PC families in FaPaCa.

RESULTS

So far, 21 families fulfilled the criteria for partaking in FaPaCa. In 11 families, PC represented the sole tumor entity. Additional tumors included malignant melanoma in 5, breast cancer in 3, and prostatic, colon or lung cancer in 2 families. Compared to the preceding generation, a younger age at diagnosis of PC was observed in the offspring of PC patients (offspring median 53 years vs. parents median 75.5 years).

CONCLUSION

The association of PC and breast cancer, and of PC and malignant melanoma suggests predisposing mutations in the BRCA2 or CDKN2A genes in about one third of the FaPaCa families. Mutational analyses in both candidate genes may help to identify individuals who are at an increased risk for developing PC. A shift towards a younger age at diagnosis in our PC families may indicate genetic anticipation and/or changes of patterns of exogenous risk factors.

Non-invasive measurements of myocardial carbon metabolism using in vivo 13C NMR spectroscopy

Despite their prime role in maintaining contractile performance, myocardial substrate uptake, substrate preference and metabolism are difficult to assess non-invasively. The objective of the present work was to extend the scope of cardiac 13C nuclear magnetic resonance (NMR) spectroscopy to the in vivo situation ('closed-chest model') and to quantitatively appraise myocardial metabolism in vivo. For this purpose, overnight-fasted Sprague-Dawley rats received intravenous infusions of non-radioactive 13C-labeled glucose, 3-hydroxybutyrate, and acetate as markers for glycolysis, metabolism of ketone bodies and direct incorporation into tricarboxylic acid (TCA) cycle, respectively. In vivo 13C NMR spectra (at 7 T) were acquired from the myocardium with a time resolution of 6 min. At the end of the infusion experiments, tissue extracts were prepared and further analyzed by high-resolution 13C NMR spectroscopy in order to corroborate the findings obtained in vivo. Accordingly, 3-hydroxybutyrate and acetate were rapidly extracted by the myocardium and supplied 42 +/- 6 and 53 +/- 9% of the acetyl-CoA for TCA cycle operation, whereas glucose, although also well extracted, did not contribute to myocardial oxidative metabolism. Myocardial TCA cycle turnover (V(TCA)) in vivo was estimated at 1.34 +/- 0.07 micromol/min/g wet weight, myocardial oxygen consumption (MVO2) at 2.95 +/- 0.16 micromol/min/g wet weight, exchange rate between alpha-ketoglutarate and glutamate (V(x)) at 1.22 +/- 0.08 micromol/min/g wet weight and rate of glutamine synthesis (V(gln)) at 0.14 +/- 0.02 micromol/min/g wet weight. The substantial synthesis of myocardial glutamine is in contrast to experiments with isolated and saline perfused hearts. In conclusion, it is demonstrated that 13C NMR spectroscopy of the heart in intact rats is feasible and provides new quantitative insight into myocardial substrate uptake, preference and metabolism in vivo.

The use of sequential designs in genome scans for asthma susceptibility loci with affected sib pairs

We use optimized group sequential study designs to analyze data from two genome scans (German and CSGA) for asthma susceptibility loci with affected sib pairs from Genetic Analysis Workshop (GAW) 12. Results are compared with those from a fixed sample design and the sequential probability ratio test (SPRT). The SPRT does not reach significance at any position. Using the fixed sample design, evidence for linkage is found on chromosomes 6 and 9 in the German and on chromosome 1 in the CSGA scan. The group sequential designs identify the same regions on chromosomes 1 and 6 with a reduced sample size.

A bivariate Haseman-Elston method and application to the analysis of asthma-related phenotypes on chromosome 5q

We propose a bivariate combination of different Haseman-Elston (HE) methods for model free linkage analysis of quantitative traits. Adjustments for correlations of phenotypes and sibship sizes > 2 are performed using generalized estimating equations (GEE). All calculations are carried out with freely available software packages. We illustrate the application of standard HE methods, the unified HE method, and our novel approach to asthma-associated quantitative traits from the COAG-Perth data set [Palmer et al., 1998, Am J Respir Crit Care Med 158:1825-30]. Our multipoint analyses provide evidence for linkage between log IgE levels adjusted for age, gender and antigen-specific IgE titers. Our results are consistent with previous findings that suggest the existence of loci regulating asthma-associated quantitative traits in the 5q31-33 chromosomal region. Simulation studies are required to compare the power of our novel bivariate HE with other HE approaches and the variance component method.

No evidence for involvement of alleles of the 825-C/T polymorphism of the G-protein subunit beta 3 in body weight regulation

The 825-C/T polymorphism of the beta 3 subunit of the heterotrimeric G protein gene (GNB3) has been shown to be associated with essential hypertension in humans. Recently, it was also reported that the 825-T allele has a higher frequency in obese than non-obese hypertensives suggesting that the primary effect of this allele is on body weight. The association to hypertension might merely be a secondary effect of the higher weight of the respective allele carriers. To investigate an involvement of the 825-T allele in body weight regulation in young individuals, we evaluated allele frequencies in 440 extremely obese children and adolescents (82.9% had a body mass index [BMI] > or = 99th percentile), 51 obese students (BMI > or = 90th percentile), 110 normal weight students (BMI between 40th and 60th percentile) and 144 underweight students (BMI < or = 15th percentile). The study groups were genotyped by polymerase chain reaction with subsequent restriction fragment length polymorphism analysis (PCR-RFLP). The one-sided Yates-corrected chi(2)-test and the Cochran-Armitage trend test for association were performed. Tests for association were negative. The 825-T allele frequencies were similar in the four study groups belonging to different weight ranges (extreme early onset obesity: 0.29; obesity: 0.28; normal weight: 0.35; underweight: 0.32). Similarly, genotype frequencies did not differ between the groups. We concluded that the 825-T allele of the GNB3 does not play a major role in weight regulation in German children, adolescents and young adults.

Specific binding of Ro 09-0198 (cinnamycin) to phosphatidylethanolamine: a thermodynamic analysis

Ro 09-0198 (cinnamycin) is a tetracyclic peptide antibiotic that is used to monitor the transbilayer movement of phosphatidylethanolamine (PE) in biological membranes during cell division and apoptosis. The molecule is one of the very rare examples where a small peptide binds specifically to a particular lipid. In model membranes and biological membranes containing phosphatidylethanolamine, Ro 09-0198 forms a 1:1 complex with this lipid. We have measured the thermodynamic parameters of complex formation with high sensitivity isothermal titration calorimetry and have investigated the structural consequences with deuterium and phosphorus solid-state NMR. Complex formation is characterized by a large binding constant, K0, of 10(7) to 10(8) M(-1), depending on the experimental conditions. The reaction enthalpy, DeltaHdegrees, varies between zero at 10 degrees C to strongly exothermic -10 kcal/mol at 50 degrees C. For large vesicles with a diameter of approximately 100 nm, DeltaHdegrees decreases linearly with temperature and the molar heat capacity of complex formation can be evaluated as = -245 cal/mol, indicating a hydrophobic binding mechanism. The free energy of binding is DeltaGdegrees = -10.5 kcal/mol and shows only little temperature dependence. The constancy of DeltaGdegrees together with the distinct temperature-dependence of DeltaHdegrees provide evidence for an entropy-enthalpy compensation mechanism: at 10 degrees C, complex formation is completely entropy-driven, at 50 degrees C it is enthalpy-driven. Varying the PE fatty acid chain-length between 6 and 18 carbon atoms produces similar binding constants and DeltaHdegrees values. Addition of Ro 09-0198 to PE containing bilayers eliminates the typical bilayer structure and produces 2H- and 31P-NMR spectra characteristic of slow isotropic tumbling. This reorganization of the lipid matrix is not limited to PE but also includes other lipids.

The exocytotic signaling pathway induced by nerve growth factor in the presence of lyso-phosphatidylserine in rat peritoneal mast cells involves a type D phospholipase

Nerve growth factor (NGF) has been previously shown to induce exocytosis in rat peritoneal mast cells (RPMCs) in the presence of lyso-phosphatidylserine (lysoPS) by interacting with high-affinity NGF receptors of the TrkA-type. In RPMCs, type D phosphatidylcholine-selective phospholipases (PLDs) have been postulated to be involved in some exocytotic signaling pathways induced by different agonists. The aim of the present study was to assess a putative functional role of PLD for NGF/lysoPS-induced exocytosis in RPMCs. In 1-[14C]palmitoyl-2-lyso-3-phosphatidylcholine-labelled RPMCs, NGF/lysoPS stimulated the formation of diacylglycerol (DAG) and, in the presence of ethanol (1% [v/v]), phosphatidylethanol (PEtOH). These data indicate PLD-activation by NGF/lysoPS in RPMCs. Preincubation of RPMCs for 2 min with ethanol, an inhibitor of PLD-derived DAG-formation, dose-dependently (IC(50): 0.6% [v/v]) and agonist-selectively inhibited the NGF/lysoPS induced release of [3H]serotonin ([3H]5-HT) in [3H]5-HT-loaded RPMCs, confirming the functional importance of PLD-action. Exocytosis and PEtOH-production was potently inhibited by the broad-spectrum serine/threonine kinase inhibitor staurosporine and activated by the protein kinase C(PKC)-activator PMA (phorbol-12-myristate-13-acetate) suggesting a role for PKC as mediator for NGF/lysoPS-induced activation of PLD.

Evidence against the functional involvement of outwardly rectifying Cl- channels in agonist-induced mast cell exocytosis

In isolated rat peritoneal mast cells, an outwardly rectifying Cl- channel has been described. Influx of Cl- through this Cl- channel (I(Cl-(OR)) causes hyperpolarization, which facilitates Ca2+ currents through store-operated Ca2+ channels. The exocytotic effect of nerve growth factor (NGF) in the presence of lyso-phosphatidylserine strictly depends on the presence of extracellular [Ca2+]o. The aim of the present study was to assess the importance of I(Cl-(OR)) for exocytosis induced by NGF/lyso-phosphatidylserine. Therefore, we investigated the effects on NGF/lyso-phosphatidylserine-induced exocytosis of [3H]5-hydroxytryptamine ([3H]5-HT) in rat peritoneal mast cells: (a) of two inhibitors of I(Cl-(OR)) (4,4'-diisothiocyanatostilbene2,2'-disulfonic acid [DIDS] and diethylstilbestrol), and (b) of replacement of extracellular Cl- by methylsulfate. Additionally, whole-cell patch-clamp experiments (nystatin-perforated patch) were performed. Diethylstibestrol and DIDS, in concentrations sufficient to abolish the I(Cl-(OR)) (10 microM) and the replacement of (Cl-)o by methylsulfate, were ineffective in impairing the NGF/lyso-phosphatidylserine-induced [3H]5-HT-release. These findings argue against a role of outwardly rectifying Cl- channels in exocytosis induced by NGF/lyso-phosphatidylserine in rat peritoneal mast cells.

Role of potassium channels in the relaxation induced by the nitric oxide (NO) donor DEA/NO in the isolated rat basilar artery

This study investigates whether potassium ion (K+) channels are involved in the nitric oxide (NO)-induced relaxation in segments of the isolated rat basilar artery, mounted onto a wire myograph. A high extracellular K+ concentration partly inhibited the relaxant effects of the NO donors DEA/NO and SIN-1 (3-morpholino-sydnonimine). Whereas single applications of the K+ channel inhibitors tetraethyl-ammonium (10(-3) M), glibenclamide (10(-6) M), 4-aminopyridine (10(-3) M), or BaCl(2) (5 x 10(-5) M) did not affect the responses to DEA/NO, a combination of these inhibitors reduced the effects of DEA/NO. These data suggest, that the relaxant effects of NO donors are partly mediated via activation of K+channels. Different K+ channel types seem to be involved that function in a redundant manner and compensate for each other.

Lack of association between endoglin intron 7 insertion polymorphism and intracranial aneurysms in a white population: evidence of racial/ethnic differences

BACKGROUND AND PURPOSE

Endoglin is a component of the transforming growth factor-beta receptor complex and is predominantly expressed on cell surfaces of endothelial cells. A polymorphism of the endoglin gene has previously been found to be associated with the occurrence of intracranial aneurysms in a Japanese population. In our study, we investigated whether this polymorphism is associated with the development of cerebral aneurysm in a white population.

METHODS

The study population consisted of 121 white patients who had been treated for intracranial aneurysms, 124 healthy white blood donors, and 15 Japanese volunteers. Exon 7 of the endoglin gene and adjacent intronic sequences were amplified by polymerase chain reaction and analyzed by using an automated laser fluorescence detection system.

RESULTS

A well-known insertion polymorphism (5'-TCCCCC-3', starting 23 bp distal from the 3' end of exon 7) was identified. The allele frequencies of the polymorphism were 35 (14.5%) of 242 alleles in the aneurysm group and 35 (14.1%) of 248 alleles in the white control group, which does not represent a statistically significant difference (P>0.85). The sequence of the polymorphism is complementary to that reported in the previously mentioned Japanese study. However, the 2 polymorphisms are identical. Under this assumption, the allele frequencies differ significantly among the Japanese controls in that particular study and the white controls in our study (27.8% versus 14.1%, respectively; P=0.0003).

CONCLUSIONS

The genetic polymorphism in the vicinity of 3' end of exon 7 in the endoglin gene was not significantly associated with the occurrence of intracranial aneurysms in the white population. There are ethnic-related differences of allele frequencies between our white controls and the previously reported Japanese controls.

Optimized group sequential study designs for tests of genetic linkage and association in complex diseases

The study of genetic linkage or association in complex traits requires large sample sizes, as the expected effect sizes are small and extremely low significance levels need to be adopted. One possible way to reduce the numbers of phenotypings and genotypings is the use of a sequential study design. Here, average sample sizes are decreased by conducting interim analyses with the possibility to stop the investigation early if the result is significant. We applied optimized group sequential study designs to the analysis of genetic linkage (one-sided mean test) and association (two-sided transmission/disequilibrium test). For designs with two and three stages at overall significance levels of.05 and.0001 and a power of.8, we calculated necessary sample sizes, time points, and critical boundaries for interim and final analyses. Monte Carlo simulation analyses were performed to confirm the validity of the asymptotic approximation. Furthermore, we calculated average sample sizes required under the null and alternative hypotheses in the different study designs. It was shown that the application of a group sequential design led to a maximal increase in sample size of 8% under the null hypothesis, compared with the fixed-sample design. This was contrasted by savings of up to 20% in average sample sizes under the alternative hypothesis, depending on the applied design. These savings affect the amounts of genotyping and phenotyping required for a study and therefore lead to a significant decrease in cost and time.

Mapping extracellular pH in rat brain gliomas in vivo by 1H magnetic resonance spectroscopic imaging: comparison with maps of metabolites

The value of extracellular pH (pH(e)) in tumors is an important factor in prognosisand choice of therapy. We demonstrate here that pH(e) can be mappedin vivo in a rat brain glioma by (1)H magnetic resonance spectroscopic imaging (SI) of the pH buffer (+/-)2-imidazole-1-yl-3-ethoxycarbonylpropionic acid (IEPA). (1)H SI also allowed us to map metabolites, and, to better understand the determinants of pH(e), we compared maps of pH(e), metabolites, and the distribution of the contrast agent gadolinium1,4,7,10-tetraazacyclododecane-N,N',N",N"'-tetraaceticacid (Gd-DOTA). C6 cells injected in caudate nuclei of four Wistar rats gave rise to gliomas of approximately 10 mm in diameter. Three mmols of IEPA were injected in the right jugular vein from t = 0 to t = 60 min. From t = 50 min to t = 90 min, spin-echo (1)H SI was performed with an echo time of 40 ms in a 2.5-mm slice including the glioma (nominal voxel size, 2.2 microl). IEPA resonances were detected only within the glioma and were intense enough for pH(e) to be calculated from the chemical shift of the H2 resonance in almost all voxels of the glioma. (1)H spectroscopic images with an echo time of 136 ms were then acquired to map metabolites: lactate, choline-containing compounds (tCho), phosphocreatine/creatine, and N-acetylaspartate. Finally, T(1)-weighted imaging after injection of a bolus of Gd-DOTA gave a map indicative of extravasation. On average, the gradient of pH(e) (measured where sufficient IEPA was present) from the center to the periphery was not statistically significant. Mean pH(e) was calculated for each of the four gliomas, and the average was 7.084 +/- 0.017 (+/- SE; n = 4 rats), which is acid with respect to pH(e) of normal tissue. After normalization of spectra to their water peak, voxel-by-voxel comparisons of peak areas showed that N-acetylaspartate, a marker of neurons, correlated negatively with IEPA (P < 0.0001) and lactate (P < 0.05), as expected of a glioma surrounded by normal tissue. tCho (which may indicate proliferation) correlated positively with pH(e) (P < 0.0001). Lactate correlated positively with tCho (P < 0.0001), phosphocreatine/creatine (P < 0.001), and Gd-DOTA (P < 0.0001). Although lactate is exported from cells in association with protons, within the gliomas, no evidence was observed that pH(e) was significantly lower where lactate concentration was higher. These results suggest that lactate is produced mainly in viable, well-perfused, tumoral tissue from which proton equivalents are rapidly cleared.

Treatment of alopecia areata in C3H/HeJ mice with the topical immunosuppressant FK506 (Tacrolimus)

Alopecia areata-like hair loss has been observed in C3H/HeJ mice and can be defined as a tissue-restricted T cell mediated disease of the hair follicle. Because FK506 has been described as suppressing T cell mediated autoimmune diseases, we addressed the question whether topical treatment of C3H/HeJ mice with FK506 has a beneficial effect on alopecia areata (AA). For this purpose six C3H/HeJ mice with AA were treated topically with 0.1% FK506 ointment, four mice received the vehicle only. Four of six FK506-treated mice showed complete hair regrowth, whereas 1/4 vehicle-treated mice regrew hair. Mice treated successfully with FK506 had reduced perifollicular infiltrates of CD4+ and CD8+ cells and a decreased expression of MHC class I and II and ICAM-1 on hair follicle epithelium, compared to control mice. We conclude that topical treatment with FK506 is able to induce hair regrowth in AA of C3H/HeJ mice, most likely by suppressing the T cell mediated immune response.

No association of three polymorphisms in the alpha-2-macroglobulin and lipoprotein related receptor genes with multiple sclerosis

Alpha-2-macroglobulin (A2M) is a proteinase inhibitor involved in deactivation of cytokines and modulation of antigen-mediated immune responses. Based on its role in inflammatory and neurodegenerative disorders, we investigated the role of A2M and its receptor low-density lipoprotein receptor-related protein (LRP) for the development of multiple sclerosis (MS). We analyzed the frequency of two polymorphisms in the A2M (Val 1000 Ile, Exon 18 del), and one polymorphism in the LRP (A216V) gene in a case control study involving 326 MS patients, and 290 controls, all defined for the expression of HLA-DR15. No association was found for any of the three polymorphism with MS. Furthermore, no differences in serum A2M levels were detected between MS patients and controls. The results do not suggest a contribution of A2M and LRP to the development of MS.

[Comparison of sonographic weight estimation to actual birth weight: a retrospective analysis]

AIM

This retrospective study aims at determining the accuracy of sonographic estimation of birth weight based on ultrasound examinations performed at the department of gynaecology of Philipps University at Marburg, Germany.

METHOD

630 children were born at the university department of gynaecology during the first six months of 1998. 519 babies had been examined sonographically and their birth weight estimated within ten days prior to delivery. 176 (33,91 %) of these examinations were carried out by experienced sonographers complying to the level II standard of performance set out by DEGUM. 343 (66.09 %) of examinations were performed by less experienced junior doctors at the time of the mothers' admission to the delivery room. Two reference tables published by Hansmann und Ferrero were used to estimate birth weight.

RESULTS

The lower and upper quartile of deviation between estimated weight and actual weight came to -200 g and + 200 g using the Hansmann method and -180 g and + 220 g respectively based on the method of Ferrero. It has to be noted that even greater differences occurred: the 10 % least exact estimates deviated by 500 g and more. The difference between estimated and actual weight increased with the length of pregnancy. The fully trained physician (DEGUM II) tended to estimate the birth weight more accurately. The average birth weight estimated sonographically was lower in "DEGUM II-babies" than that of children whose weight was estimated at the point of admission to the delivery room (Mann-Whitney p < 0,0001). Junior doctors showed a tendency to over-estimate the birth weight of babies actually being underweight. The opposite happened with babies who presented a relatively higher birth weight: their projected birth weight was underestimated. On the other hand, the regression line of the sonographic estimations of birth weight performed by the expert (level II DEGUM) fit to the expected bisector of the angle (Passing-Bablock p > 0,05).

CONCLUSION

When clinical decisions are based on estimated values of birth weight, the possible deviation of this value from the actual weight has to be taken into account. In our study this difference came up to 500 g independent of the level of the examiner's ultrasonographic training.