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111.
Steven A. Narod Dilys M. Parry Jillian Parboosingh Gilbert M. Lenoir Martin Ruttledge Georges Fischer Roswell Eldridge Robert L. Martuza Marina Frontali Jonathan Haines James F. Gusella Guy A. Rouleau 《American journal of human genetics》1992,51(3):486-496
Neurofibromatosis type 2 (NF2) is an autosomal dominant syndrome characterized by the development of vestibular schwannomas and other tumors of the nervous system, including cranial and spinal meningiomas, schwannomas, and ependymomas. The presence of bilateral vestibular schwannomas is sufficient for the diagnosis. Skin manifestations are less common than in neurofibromatosis type 1 (NF1; von Recklinghausen disease). The apparent clinical distinction between NF1 and NF2 has been confirmed at the level of the gene locus by linkage studies; the gene for NF1 maps to chromosome 17, whereas the gene for NF2 has been assigned (in a single family) to chromosome 22. To increase the precision of the genetic mapping of NF2 and to determine whether additional susceptibility loci exist, we have performed linkage analysis on 12 families with NF2 by using four polymorphic markers from chromosome 22 and a marker at the NF1 locus on chromosome 17. Our results confirm the assignment of the gene for NF2 to chromosome 22 and do not support the hypothesis of genetic heterogeneity. We believe that chromosome 22 markers can now be used for presymptomatic diagnosis in selected families. The NF2 gene is tightly linked to the D22S32 locus (maximum lod score 4.12; recombination fraction 0). A CA-repeat polymorphism at the CRYB2 locus was the most informative marker in our families (lod score 5.99), but because the observed recombination fraction between NF2 and CRYB2 was 10 cM, predictions using this marker will need to be interpreted with caution. 相似文献
112.
Catalytic properties of hen egg white lysozyme were analyzed during the renaturation of the enzyme from completely reduced and denatured material. The formation of intermediate folding products and the generation of native lysozyme was monitored by acetic acid/urea electrophoresis. The results showed that during the beginning of renaturation almost all reduced and denatured lysozyme is converted to forms possessing lower compactness than native lysozyme, probably as a result of formation of only one or two disulfide bonds. Kinetic analysis of lysozyme during renaturation showed that the generation of lysozyme with four disulfide bonds was not necessarily equivalent to the formation lysozyme with native-like catalytic properties. It appeared that the formation rate of the structures of the structures of the substrate binding site and of the catalytic site were limited by the generation of four disulfide bonds containing lysozyme. The catalytic properties of intermediate folding products made it evident that the final structures of the substrate binding site and of the catalytic site were formed after the generation of all disulfide bonds. 相似文献
113.
Bovine parathyroid hormone (PTH) 1-34 [bPTH(1-34)] and human PTH related protein [hPTHrP(1-34)] stimulated cAMP accumulation in opossum kidney (OK) cells with Km of 5 x 10(-9) M, but inhibition of phosphate uptake was obtained with 17-fold lower Km of 3 x 10(-10) M. Phosphate uptake was partially inhibited with [Nle8.18Tyr34]bPTH(3-34)NH2 without concomitant cAMP stimulation. With hPTHrP(7-34)NH2, cAMP accumulation was increased in parallel to inhibition of phosphate uptake. [D-Trp12Tyr34]bPTH(7-34)NH2 and [Tyr34]hPTH(7-34)NH2 had no agonist activity on cellular cAMP and inhibition of phosphate uptake. bPTH(1-34)-stimulated cAMP accumulation was antagonized by [Nle8.18Tyr34]bPTH(3-34)NH2, [D-Trp12Tyr34]bPTH(7-34)NH2, hPTHrP(7-34)NH2 and [Tyr34]hPTH(7-34)NH2 with Ki of 1.4 x 10(-7), 2 x 10(-7), 4.7 x 10(-7) and 3.7 x 10(-6) M, respectively. But [Nle8.18Tyr34]bPTH(3-34)NH2 and [D-Trp12Tyr34]bPTH(7-34)NH2 reversed the inhibition of phosphate uptake only marginally, and hPTHrP(7-34)NH2 and [Tyr34]hPTH(7-34)NH2 were inactive. With hPTHrP(1-34) the Ki for cAMP accumulation of [Nle8,18Tyr34]bPTH(3-34)NH2 and hPTHrP(7-34)NH2 were 1.9 x 10(-7) and 7.2 x 10(-7) M, and inhibition of phosphate uptake was partially reversed with [Nle8,18Tyr34]bPTH(3-34)NH2, but not with hPTHrP(7-34)NH2. The present results indicate that truncated hPTHrP(7-34)NH2, unlike [Tyr34]hPTH(7-34)NH2 and [D-Trp12Tyr34]bPTH(7-34)NH2, elevates cellular cAMP and inhibits phosphate uptake. bPTH(1-34)- and hPTHrP(1-34)-evoked cAMP accumulation is suppressed by PTH and PTHrP fragments while inhibition of phosphate uptake remains largely unaltered. 相似文献
114.
M. Engelhard K. D. Kohl K. H. Müller B. Hess J. Heidemeier M. Fischer F. Parak 《European biophysics journal : EBJ》1990,19(1):11-18
Bacteriorhodopsin (bR), converted by deionization to the blue form was reconstituted to the active purple membrane by the addition of Fe2+ or Fe3+ ions. 57Fe Mossbauer spectra of these samples were measured at different pH values (pH 3.9, pH 5.0 and pH 7.0) and at temperatures ranging from 4 K to 300 K. The hyperfine parameters reveal two iron environments with oxygen atoms in the neighbourhood of iron. Iron type 1 is in the 3+ high spin state. It is bound to acid side chains of the protein and/or the phosphate groups of the lipids. Iron type 2 is in the 2+ high spin state and is linked to carboxy groups of the protein in a rather unspecific way. Dynamics as measured by Mossbauer spectroscopy show that the purple membrane becomes flexible only above 220 K. At the interface between membrane and bulk water the mobility is comparable to that of proteins with hydrophilic surfaces. The photocycle of Fe 3+-bR is slowed down compared to native bR. 3–5 Fe3+/bR are sufficient to inhibit the photocycle turnover by one order of magnitude. This specific effect is also found with Cr3+, though it is less pronounced. Mössbauer spectra of Fe3+-bR at 4 K reveal that iron nuclei are spin-coupled, indicating their close spatial proximity. It is proposed that iron trinuclear clusters interact with the proton uptake site of bR.
Offprint requests to: M. Engelhard 相似文献
115.
Molecular size characterization of bacterial capsular polysaccharide vaccines by high performance liquid chromatography 总被引:2,自引:0,他引:2
Bacterial capsular polysaccharides are major virulence factors and some are used as vaccinal antigens. Their molecular size is an important physicochemical criterion which correlates with immunogenicity. This article describes a new application of high performance liquid chromatography (HPLC), based on molecular sieving, for such an evaluation. This HPLC method is rapid, accurate, reproducible, requires only very low amounts of product and presents good correlation with conventional gel permeation chromatography. 相似文献
116.
117.
H. E. Valentin A. Schönebaum A. Steinbüchel 《Applied microbiology and biotechnology》1996,46(3):261-267
A recombinant strain of Pseudomonas putida GPp104 (pHP1014::E146), which expressed the polyhydroxyalkanoic acid (PHA) synthase of Thiocapsa pfennigii exhibiting an unusual substrate specificity at a high level was incubated in two-stage batch or fed-batch accumulation experiments
with 5-hydroxyhexanoic acid (5HHx) as carbon source in the second cultivation phase, copolyesters of 3-hydroxybutyric acid
(3HB) plus 5HHx, or of 3HB, 3-hydroxyhexanoic acid (3HHx) plus 5HHx were accumulated as revealed by gas-chromatographic and
13C-NMR spectroscopic analysis. When the recombinant P. putida GPp104 was incubated with 4-hydroxyheptanoic acid (4HHp) as carbon source in the second cultivation phase, a copolyester
consisting of 3HB, 3-hydroxyvaleric acid and 3- and 4-hydroxyheptanoic acid accumulated. Providing 4-hydroxyoctanoic acid
as carbon source in the second cultivation phase led to the accumulation of a polyester that contained 1–2 mol% 4-hydroxyoctanoic
acid besides 3-hydroxyoctanoic acid, 3HHx, 3-hydroxyvaleric acid and 3HB. In addition to PHA containing these new constituents,
PHA with 4-hydroxyvaleric acid was accumulated from laevulinic acid. Eleven strains from five genera have been also analysed
for their ability to utilize different carbon sources for colony growth, which might serve as potential precursors for the
biosynthesis of PHA with unusual constituents. Although most of the carbon sources were utilized by some strains for colony
growth, accumulation experiments gave no evidence for the accumulation of new PHA by these wild-type strains.
Received: 22 April/Received revision: 23 May 1996/Accepted: 2 June 1996 相似文献
118.
Prion protein (PrP) with amino-proximal deletions restoring susceptibility of PrP knockout mice to scrapie. 总被引:35,自引:3,他引:32
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M Fischer T Rülicke A Raeber A Sailer M Moser B Oesch S Brandner A Aguzzi C Weissmann 《The EMBO journal》1996,15(6):1255-1264
The 'protein only' hypothesis postulates that the prion, the agent causing transmissible spongiform encephalopathies, is PrP(Sc), an isoform of the host protein PrP(C). Protease treatment of prion preparations cleaves off approximately 60 N-terminal residues of PrP(Sc) but does not abrogate infectivity. Disruption of the PrP gene in the mouse abolishes susceptibility to scrapie and prion replication. We have introduced into PrP knockout mice transgenes encoding wild-type PrP or PrP lacking 26 or 49 amino-proximal amino acids which are protease susceptible in PrP(Sc). Inoculation with prions led to fatal disease, prion propagation and accumulation of PrP(Sc) in mice expressing both wild-type and truncated PrPs. Within the framework of the 'protein only' hypothesis, this means that the amino-proximal segment of PrP(C) is not required either for its susceptibility to conversion into the pathogenic, infectious form of PrP or for the generation of PrP(Sc). 相似文献
119.
120.
Johannes B Salnitzki VP Haller H Wilke D Fischer F Schlykova L 《Journal of gravitational physiology : a journal of the International Society for Gravitational Physiology》1995,2(1):P107-P108
The relation between the results of laboratory tests and results of the interesting professional work is a very difficult one. The same is true for the relation between training and real performance. The pilot controlled MIR-docking manoeuvre is in reality a very seldom but very important one. The training of this manoeuvre is a very special professional work and only for cosmonauts available. But the objective estimation of the performance and the used objective and subjective needs is nevertheless necessary. Even for the subjective "stress"-feelings during task solving it is often impossible to get reliable data without any physiological measurements. The use of electrodes, cables and equipments is hardly limited during real work. Sometimes only the voice is available over more or less quality communication channels. So it is the case during the training and the real pilot controlled MIR-docking manoeuvre. Based on findings in the literature and own experiments analyzing the relation between fundamental voice frequency (F0) and subjective stress feelings we tested the hypothesis that a on-line measurement of F0 can be used for stress evaluation during standardised training sessions of MIR-docking manoeuvres. 相似文献