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Biomedical subjects

H Bürger

Publications and source records attributed to H Bürger.

At least 73 records · Page 4Linked to original sources
PubMed1998

High Resolution FTIR Study of the nu5 Bands of HSiD3 and H120SnD3

High resolution Fourier Transform spectra of HSiD3 and monoisotopic H120SnD3 have been recorded in the region of the nu5 fundamental at 850.68 and 646.90 cm-1 with a resolution of 3.3 and 2.8 x 10(-3) cm-1, respectively. About 2000 rovibrational transitions of each species have been assigned and fitted to two different reductions of the effective Hamiltonian, with sigma(Fit) = 1.2 x 10(-4) (HSiD3) and 1.4 x 10(-4) cm-1 (H120SnD3). The two sets of parameters were shown to be equivalent, and relations between parameters belonging to different reductions are perfectly fulfilled. Furthermore the ground state constants C0 and DK0 have been determined for the first time. For consistency the previously measured data belonging to the nu5 band of H70GeD3 have been refitted, sigma(Fit) = 1.6 x 10(-4) cm-1, on the basis of improved ground state parameters including the h'3 term accounting for the splitting of the K = 3 level. Copyright 1998 Academic Press.

Journal Article↗
PubMed1998

High-Resolution FTIR Study of Thiocarbonyl Difluoride SCF2

High-resolution ( approximately 3 x 10(-3) cm-1) FTIR spectra of the planar SCF2 molecule have been recorded in the range of the four lowest-lying fundamentals nu2 (789.535 cm-1), nu3 (526.697 cm-1), nu5 (419.546 cm-1), and nu6 (623.187 cm-1). For each band 4500-7500 transitions have been assigned and fitted to a standard Watson-type Hamiltonian up to quartic terms, sigma(Fit) approximately 3.5 x 10(-4) cm-1. No indication of rovibrational perturbations was found, excited state rotational and centrifugal distortion constants being close to their ground state values. Ground state parameters previously determined from microwave spectra were, in part, improved by a merge of the appropriately weighted microwave data and approximately 10 000 ground state combination differences that were obtained from the nu4 band and spanning J and Ka values of 88 and 49, respectively. Copyright 1998 Academic Press.

Journal Article↗
PubMed1998

Diode Laser and FTIR Spectroscopy of BrCN Isotopomers in the Region of the nu3 Band.

The nu3 fundamental band (C-N stretch) and four associated hot bands (01(1)1-01(1)0, 10(0)1-10(0)0, 02(0)1-02(0)0, and 02(2)1-02(2)0) of natural 79/81Br12C14N have been recorded and analyzed in the 4.8-µm region using an FTIR spectrometer. Analyses of the same hot bands, previously recorded using a diode laser spectrometer, are also presented for the 13C and 15N isotopically labeled species. Copyright 1998 Academic Press.

Journal Article↗
PubMed1998

Analysis of the Rotational Spectra of SiH3CN and Its Isotopomers: Experimental and Ab Initio Determinations of the Dipole Moment and the Structure.

The ground state rotational spectra of SiH3CN and its 29Si, 30Si, 13C, 15N, d1, d2, and d3 isotopic species have been measured by Fourier transform microwave spectroscopy and by millimeterwave spectroscopy. Accurate rotational, centrifugal distortion, and 14N and D nuclear quadrupole coupling constants have been derived. The dipole moment of the parent species has also been measured, µ = 3.4400(42) D. The structure, force field, dipole moment, and nuclear quadrupole coupling constants have been calculated ab initio at the SCF, MP2, and B3LYP levels using triple zeta polarized basis sets. The experimental ro, rs, and rz structures have been determined. An approximate equilibrium structure has been obtained by combining the experimental results and the ab initio calculations: re(C&tbond;N) = 1.159 Å, re(Si&sbond;C) = 1.848 Å, re(Si&sbond;H) = 1.470 Å, and angle(HSiC) = 107.4 degrees. Copyright 1998 Academic Press.

Journal Article↗
PubMed1998

Fourier Transform Spectroscopy of the nu3 and nu6 Bands of D3Si35Cl: Rovibrational Constants of the v = 0, v3 = 1, and v6 = 1 States.

The nu3 and nu6 infrared bands near 500 cm-1 of monoisotopic D3Si35Cl have been studied with a resolution of 3.3 x 10(-3) cm-1. More than 800 transitions of nu3 and 2600 of nu6 have been assigned and fitted to ground and excited state parameters, final sigma(Fit) = 2.93 x 10(-4) cm-1. Ground state parameters up to quartic terms have been obtained. The excited state model included l(2, 2) and l(2, -1) interactions within nu6 and Coriolis x, y resonance between nu3 and nu6, interaction parameters being determined with high significance in all cases. The band centers nuo were determined, nu3 = 538.502 cm-1 and nu6 = 491.260 cm-1. Excellent agreement of experimental parameters with those from the ab initio harmonic and anharmonic force fields is noted. The transition moment ratio, ||µ3:µ6 || = 1:0.6(1), was determined by band contour simulation. Copyright 1998 Academic Press.

Journal Article↗
PubMed1998

High-Resolution Study of the First Stretching Overtones of H3Si79Br.

The Fourier transform infrared spectrum of monoisotopic H3Si79Br (resolution 7.7 x 10(-3) cm-1) was studied from 4200 to 4520 cm-1, in the region of the first overtones of the Si-H stretching vibration. The investigation of the spectrum revealed the presence of two band systems, the first consisting of one parallel (nu0 = 4340.2002 cm-1) and one perpendicular (nu0 = 4342.1432 cm-1) strong component, and the second of one parallel (nu0 = 4405.789 cm-1) and one perpendicular (nu0 = 4416.233 cm-1) weak component. The rovibrational analysis shows strong local perturbations for both strong and weak systems. Seven hundred eighty-one nonzero-weighted transitions belonging to the strong system [the (200) manifold in the local mode picture] were fitted to a simple model involving a perpendicular component interacting by a weak Coriolis resonance with a parallel component. The most severely perturbed transitions (whose ||obs-calc || values exceeded 3 x 10(-3) cm-1) were given zero weights. The standard deviations of the fit were 1.0 x 10(-3) and 0.69 x 10(-3) cm-1 for the parallel and the perpendicular components, respectively. The weak band system, severely perturbed by many "dark" perturbers, was fitted to a model involving one parallel and one perpendicular band, connected by a Coriolis-type resonance. The K" . DeltaK = +10 to +18 subbands of the perpendicular component, which showed very high observed - calculated values ( approximately 0.5 cm-1), were excluded from this calculation. The standard deviations of the fit were 11 x 10(-3) and 13 x 10(-3) cm-1 for the parallel and the perpendicular components, respectively. Copyright 1998 Academic Press.

Journal Article↗
PubMed1998

Ab Initio Calculations and High-Resolution Spectroscopy of the Bending Pentad of SiH2D2 in the 10-16 µm Region.

The SiH2D2 asymmetric top has nine vibrational modes, five of them forming a pentad strongly perturbed by Coriolis interactions. High-level ab initio calculations of SiH2D2 have been performed which yield numerous spectroscopic parameters related to the harmonic and anharmonic force fields. The bending pentad comprising nu4(A1), nu7(B1), nu5(A2), nu9(B2), and nu3(A1) has been studied by high-resolution Fourier transform spectroscopy; the region 600-1050 cm-1 has been investigated with a resolution of ca. 4 x 10(-3) cm-1. Raman BOXCARS spectroscopy has been used for the infrared inactive nu5 band. The Raman apparatus function was 0.0054 cm-1. Assignments of about 4000 transitions including all bands have been made, mostly employing ground state combination differences techniques, and a global fit has been performed. The fundamentals nu4 (681.624 cm-1), nu7 (742.640 cm-1), nu5 (842.381 cm-1), nu9 (859.750 cm-1), and nu3 (942.741 cm-1) are strongly coupled by A-, B-, and C-type Coriolis interactions, and ab initio predictions of these interaction parameters were used to set up a network of interactions that was refined by the experimental data. The global standard deviation for the entire body of data is 7.1 x 10(-4) cm-1. Satisfactory synthetic spectra which are very sensitive to relative signs of dipole moment derivatives and Coriolis interaction constants were obtained with the guidance of ab initio calculations. Finally, fair to good agreement of experimental and ab initio calculated molecular parameters was obtained. For the first time, a complete analysis of the pentad of SiH2D2 in the 10-16 µm region has been carried out. A full set of rovibrational parameters is given for these five interacting levels, including first and second order Coriolis interaction constants. Copyright 1998 Academic Press.

Journal Article↗
PubMed1998

Telomerase activity in human proliferative breast lesions.

Telomerase, a cellular reverse transcriptase, has been detected in the majority of human malignant tumors, where it provides an escape mechanism from proliferative limitations due to progressive telomere erosion with each cell division. In this study, we used a non-radioactive telomeric repeat amplification protocol (TRAP) with an internal telomerase assay standard for the detection and semiquantitative analysis of 98 single frozen sections of normal breast tissue and benign and malignant breast lesions on an automated laser-fluorescence sequencer. Telomerase activity was detected in 36 of 40 (90%) infiltrating breast carcinomas, whereas no activity was found in nonmalignant breast tissues including blunt duct adenosis, papilloma, ductal hyperplasia and atypical ductal hyperplasia. However, telomerase activity was detected in 59% of ductal in situ carcinomas, suggesting that telomerase reactivation is an early event in breast carcinogenesis. We found a positive correlation between telomerase activity levels and cell proliferation determined by MIB1 immunostaining. No correlation, however, could be demonstrated between telomerase activity and other known breast cancer prognostic indicators. Telomerase activity was also detected in 60% of fibroadenomas indicating that careful interpretation of analysis of telomerase activity in fine needle aspirates is required, since low telomerase activity may not necessarily be an indicator of malignancy in breast tissue.

Breast↗
PubMed1998

[Comparative genomic hybridization (CGH) for detecting a heretofore undescribed amplified chromosomal segment in high-grade medullary osteosarcoma].

Osteosarcoma is one of the most commonly biopsied primary tumor of bone. High-grade osteosarcomas in particular exhibit a wide spectrum of cytogenetic changes. Molecular cytogenetic studies on osteosarcomas have shown that genomic amplification, especially of both the TP53-binding MDM2 gene and the flanking SAS gene, plays an important role in the biology of these tumors. We applied CGH in order to obtain a global view of DNA-sequence losses and gains in osteosarcoma. CGH was performed on 20 high-grade medullary osteosarcomas (13 primary tumors prior to chemotherapy, 5 tumors after chemotherapy, 2 established cell lines [MB63, HOS58]) using genomic DNA of snap-frozen tumor specimens. CGH revealed DNA copy number aberrations, mostly gains, in all the tumors studied with an average of 18.5 aberrations/tumor (range 8-32). High-level amplifications were observed in all cases (average 4.1 amplifications/tumor [range 1-10]). Amplicons affecting at least five tumors were mapped to 1p21-31 (9/20 cases), 3q25-qter (6/20), 6p12-21 (6/20), 8q12-qter (10/20), 12p11-12 (9/20), 12q12-15 (enclosing MDM2 and SAS loci, 7/20). Losses were most frequently seen at 3p, 10q, 11p and 13 (all 10/20). In conclusion, our CGH data indicated that genomic amplification plays an important role in the biology of osteosarcoma. CGH demonstrated the complexity of genetic aberrations in osteosarcomas. The detection of novel non-random DNA amplifications in our study has defined regions for further targeted molecular genetic research aimed at identifying those oncogenes that are characteristic of osteosarcoma development.

Bone Neoplasms↗
PubMed1990

Osteomyelitis due to Cryptococcus neoformans in advanced age. Case report and review of literature.

In an 84-year-old man cryptococcosis with a pronounced osteomyelitic course (involvement of a rib, two thoracic vertebrae, the sacrum and a femur) was diagnosed histologically post mortem, thus directing attention to cryptococcosis in advanced age. The presumptive chronic course of the Cryptococcus neoformans (Cr. n.) infection in this patient was ascribed to chronic kidney failure, diabetes mellitus and chronic obstructive lung disease. Special reference is made to the mycological and radiological diagnosis of cryptococcosis of the bones as well as to its pathogenesis, therapy and epidemiology.

Aged↗
PubMed1985

The nucleoprotein as a possible major factor in determining host specificity of influenza H3N2 viruses.

In an attempt to assess the importance of the nucleoprotein (NP) in the determination of host specificity, a series of experiments was performed on influenza A viruses of the H3N2 subtype. We have examined rescue of mutants of A/FPV/Rostock/34 with temperature-sensitive (ts) lesions in the nucleoprotein (NP) gene by double infection of chick embryo cells with H3N2 strains isolated from different species. The ts mutants could be rescued by all avian H3N2 strains but not by any of the human H3N2 isolates. Only two of the swine H3N2 strains tested were able to rescue our mutants. The NP gene of these two swine isolates resembled the NP gene of the avian strains genetically in the hybridization test. However, their NPs reacted differently with a set of monoclonal antibodies when compared with NPs of avian H3N2 strains. Concerning multiplication in ducks they behaved like the other swine and human strains. The phosphopeptide fingerprints of all swine isolates tested were alike and were different from those of human or avian origin. Our observations are compatible with the idea that human H3N2 strains might not be able to cross the species barrier to birds directly, and possibly also not the other way around, without prior reassortment in pigs, which seem to have a broader host range concerning the compatibility of the NP gene in reassortants.

Animals↗
PubMed1985

Sequence of the nucleoprotein gene of influenza A/parrot/Ulster/73.

The nucleotide sequence of the nucleoprotein (NP) gene of the avian influenza A virus strain A/parrot/Ulster/73 (H7N1) has been determined. The gene (RNA segment 5) consists of 1565 bases. The only large open reading frame of the complementary RNA codes for a protein of 498 amino acids. A comparison of its sequence with that of three other influenza virus NPs shows that the NP of the parrot Ulster strain, although closely related to the NP of the other avian strain (A/FPV/Rostock/34), is definitely more closely related genetically to the NPs of the two human influenza strains, A/PR/8/34 and A/NT/60/68 than that of FPV. This raises the question how far the NP gene can cross the species barrier by reassortment and become adapted by mutation to the new host.

Amino Acid Sequence↗
PubMed1985

A mutant of fowl plague virus (influenza A) with an enhanced electrophoretic mobility of RNA segment 8.

A temperature-sensitive mutant (ts 1/9) obtained by undiluted passage of fowl plague virus (FPV) at 33 degrees C carried a strong ts defect in RNA segment 6 [neuraminidase (NA) gene] and a weak ts defect in RNA segment 8 [non-structural (NS) protein Although the viral proteins have normal migration rates, the NS gene migrated during polyacrylamide gel electrophoresis (PAGE) significantly faster than the NS gene of wild-type FPV, even after denaturation by glyoxal. Despite this observation, the NS gene of ts 1/9 did not carry a deletion as shown by sequence determination. There were only five base replacements which resulted in three changes in amino acids. Three of the base replacements led to a more compact secondary structure of RNA segment 8, which seems to be responsible for the faster migration rate during PAGE and which seems to resist, at least partially, the treatment with glyoxal.

Amino Acid Sequence↗
PubMed1985

Adaptation of a coculture technique to the Minitek anaerobe system.

A method to produce anaerobic conditions by coculture with a nonfermentative organism was utilized in conjunction with the Minitek anaerobe system (BBL Microbiology Systems, Cockeysville, Md.) for identification of anaerobic bacteria from clinical specimens. With the coculture method, the Minitek anaerobe identification tests could be incubated under aerobic conditions. In 1,900 individual biochemical reactions, 1,826 (96%) were identical whether anaerobic conditions were achieved by conventional or coculture techniques. In comparison with the reference identification (Virginia Polytechnic Institute and State University, Blacksburg), both systems of incubation identified 91 of 99 strains (92%) correctly. The method of incubation had an effect on identification to the genus level in 1 of 99 (1%) strains and to the species level in 3 of 99 (3%) strains.

Bacteria, Anaerobic↗